Thermoresistance adhesive and semiconductor device using the same

ABSTRACT

A thermoresistance adhesive which does not dissolve in the sealer-composing resins at the sealer molding temperature and is capable of providing a semiconductor chip/lead frame adhesive strength under shear of 1 N/4 mm 2  or greater, and including, for example, amide, imide, ester or ether linkage is suited for use in producing thermoresistance adhesive solutions and thermoresistance resin pastes, and the semiconductor chips, lead frames, films, etc., made by using such an adhesive are suited for providing low-cost semiconductor devices.

TECHNICAL FIELD

The present invention relates to a thermoresistance adhesive, athermoresistance adhesive solution, a thermoresistance resin paste, aprocess for the preparation thereof, a semiconductor chip having athermoresistance adhesive layer, a lead frame having a thermoresistanceadhesive layer, a film having a thermoresistance adhesive layer, and asemiconductor device.

BACKGROUND ART

The resin-sealed semiconductor devices are typically of the structuressuch as illustrated in FIGS. 1 to 3. A thermoresistance adhesive is usedfor bonding the inner leads of a lead frame to a semiconductor chip inthe semiconductor device of FIG. 1, or bonding the inner leads of a leadframe which doubles as a buffer coat to the chip surface in thesemiconductor device of FIG. 2. In an ordinary semiconductor deviceshown in FIG. 3, the said adhesive is utilized for bonding a lead frametab (die pad) to the back side of a chip. The structures of thesemiconductor devices of the type illustrated in FIGS. 1 and 2 arecalled lead-on-chip (LOC) structure, and the thermoresistance adhesiveused therefor is required to be capable of providing secure bonding(especially heat bonding) of the chip and lead frame and to also haveenough adhesiveness to the sealer to prevent package cracking in solderreflowing.

Recently, with advancement of miniaturization of semiconductor devices,the proportion of the chips in the semiconductor devices has increasedwhile the rate of the sealer used in such devices has decreased, andthis situation is blamed for the frequent occurrence of packagecracking, a phenomenon caused as the moisture absorbed in thethermoresistance adhesive or sealer is vaporized and expanded by theheat such as generated from soldering treatment (solder reflowing). Inorder to prevent such a phenomenon, it has been attempted to lowerhygroscopicity or elevate glass transition temperature of thethermoresistance adhesive and to split the adhesive mass into aplurality of small pieces, thereby allowing escape of the water vaporsin solder reflowing to prevent cracking (JP-A 3-109757). With theconventional adhesives, however, it has been hardly possible to provideboth secure bonding (especially heat bonding) of the chip and lead frameand enough adhesiveness to the sealer to prevent package cracking insolder reflowing.

The heat-resistant resins such as polyimide resins have already beenwidely used for surface protective films, interlaminar insulating films,etc., of semiconductor elements in the field of electronics as theseresins have excellent mechanical properties as well as high heatresistance. Recently, as means for forming an image on such polyimidefilms, attention is focussed on screen printing which can dispense withsuch steps as exposure, development and etching. A thixotropicheat-resistant resin paste composed of a filler, a binder and a solventis used for screen printing. In most of the hitherto developedthermoresistance resin pastes, fine silica particles or non-soluble finepolyimide particles are used as the filler for affording the thixotropicproperties, so that these resin pastes involve the problem that manyvoids or air cells are formed at the filler interface during heat dryingto lower the film strength. There have been developed thethermoresistance resin pastes (such as the one disclosed in JP-A2-289646) which are free of such problems and capable of forming ahigh-quality polyimide pattern by using a combination of an organicfiller (soluble filler), a binder and a solvent, in which in the courseof heat drying, the filler is first dissolved and then compatibilizedwith the binder to form a film. In production of this type of resinpaste, mechanical milling such as roll milling is required as means formixing and dispersing the fine silica particles or non-soluble polyimideparticles and a specific organic filler (soluble filler) in abinder/solvent solution. According to this method, however, dust orother ionic impurities tend to mix in the thermoresistance resin pastefrom the mixer and/or the mixing atmosphere, so that this technique wasunsuited for such uses as production of semiconductor elements and alsounsatisfactory in terms of productivity. Further, since the specificorganic filler (soluble filler) is generally produced by areprecipitation method in which a dilute polyimide resin solution issupplied into a poor solvent of the polyimide resin and the precipitatedfine solid particles are recovered, the process was complicated and lowin productivity.

DISCLOSURE OF INVENTION

An object of the present invention is to solve these problems and toprovide a thermoresistance adhesive which is capable of providing securebonding (especially heat bonding) of a chip and a lead frame and alsohas sufficient adhesiveness to the sealer to prevent package cracking insolder reflowing, a solution of such a thermoresistance adhesive, and asemiconductor chip having a thermoresistance adhesive layer, lead framehaving a thermoresistance adhesive layer, a film having athermoresistance adhesive layer, and a semiconductor device.

Another object of the present invention is to provide a thermoresistanceresin paste which is capable of affording the thixotropic properties tosaid elements with no need of using a filler such as fine silicaparticles or non-soluble polyimide particles, and also makes it possibleto form a pattern uniform in thickness, high in reliability and free ofvoids or air cells by screen printing, and a process for producing sucha thermoresistance resin paste containing few contaminants such as dustor ionic impurities with high productivity.

Thus, the present invention provides a thermoresistance adhesive to beused for bonding a semiconductor chip and a lead frame in a resin-sealedtype semiconductor device, characterized in that the said adhesive doesnot dissolve in the sealer composing resins at the sealer moldingtemperature, and that its semiconductor chip/lead frame adhesivestrength under shear is 1 N/4 mm² or greater.

The present invention further provides a thermoresistance adhesivesolution containing an organic solvent in addition to the saidcomponents of the said thermoresistance adhesive.

It is also envisaged in this invention to provide a thermoresistanceresin paste comprising (A) a heat-resistant resin having a hydroxylgroup, an amino group or a carboxyl group in the molecule, (B) fineorganic particles, (C) a crosslinking agent having functional groupschemically bondable to the said hydroxyl, amino or carboxyl group, and(D) a solvent, characterized in that before heat drying, the fineorganic particles (B) exist as a heterogeneous phase as opposed to thehomogeneous phase composed of the heat-resistant resin (A), crosslinkingagent (C) and solvent (D), and after heat drying, there is formed ahomogeneous phase containing the heat-resistant resin (A), fine organicparticles (B) and crosslinking agent (C) as essential components.

The present invention further provides a thermoresistance adhesiveobtained by drying either the said thermoresistance adhesive solution orthe said thermoresistance resin paste.

The present invention also provides a semiconductor chip having athermoresistance adhesive layer produced by providing a layer of saidthermoresistance adhesive on the circuit forming side of a semiconductorchip.

The present invention further provides a lead frame having athermoresistance adhesive layer produced by providing a layer of saidthermoresistance adhesive on the semiconductor chip-mounted side of alead frame.

The present invention further provides a film having a thermoresistanceadhesive layer produced by providing a layer of said thermoresistanceadhesive on one or both sides of a support film.

The present invention is also intended to provide a semiconductor devicein which the plural inner leads of a lead frame are bonded to thecircuit-forming side of a semiconductor chip by the saidthermoresistance adhesive, and the semiconductor chip and the innerleads of the lead frame are electrically connected by wire bonding, saidsemiconductor chip being sealed by a sealant.

The present invention further provides a process for producing athermoresistance resin paste which comprises mixing (I) a heat-resistantresin A soluble in the solvent of (III) at room temperature and at theheat drying temperature, (II) a heat-resistant resin B which isinsoluble in the solvent of (III) at room temperature but soluble at theheat drying temperature, and (III) a solvent, dissolving the saidmaterials by heating, and cooling the obtained soluble to have the fineparticles of the heat-resistant resin B of (II) precipitated anddispersed in the solution of the heat-resistant resin A of (I) and thesolvent of (III).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a structure of the semiconductordevice of this invention in which the semiconductor chip is positionedon the lower side of the lead frame.

FIG. 2 is a schematic illustration of a structure of the semiconductordevice of this invention in which the semiconductor chip is alsopositioned on the lower side of the lead frame.

FIG. 3 is a schematic illustration of a structure of the semiconductordevice of this invention in which the semiconductor chip is positionedon the upper side of the lead frame.

BEST MODE FOR CARRYING OUT THE INVENTION

As a result of the studies on the relationship between package crackingin solder reflowing of a moisture-absorbed semiconductor device andadhesiveness of the thermoresistance adhesive used therefor, the presentinventors found that the main causative factor of package cracking issolubility of the adhesive in the sealer-composing resins at the sealermolding temperature, rather than hygroscopicity or glass transitiontemperature of the adhesive, and that the problem of such packagecracking can be overcome by using a thermoresistance adhesive which doesnot dissolve in the sealer-composing resins at the sealer moldingtemperature. This finding provides the basis of the present invention.

Generally, in case of using a thermoresistance adhesive of the typewhich dissolves in the sealer-composing resins at the sealer moldingtemperature, exfoliation is liable to take place at the interfacebetween the adhesive and the sealer even before the solder reflowingstep, encouraging the tendency for package cracking to occur. Further,such a thermoresistance adhesive which dissolves in the sealer-composingresins forms a molten fluid with the sealer under high temperature (200°C. or above) in solder reflowing, which tends to cause blistering andcracking of the package. On the other hand, simple affording ofthermosetting properties to the thermoresistance adhesive as means forlowering its solubility in the sealer-composing resins, althougheffective for improving the package cracking tendency, poses the problemthat the adhesive force (especially in heat bonding) of said adhesive tothe semiconductor chip or lead frame is weakened. It has never beenanticipated that use of a thermoresistance adhesive which does notdissolve in the sealer-composing resins at the sealer moldingtemperature and has adhesiveness (especially heat bondability) to thesemiconductor chip or lead frame should be effective for improvingpackage cracking resistance of the semiconductor devices.

The present invention comprehends the following embodiments.

(1) A thermoresistance adhesive to be used for bonding a semiconductorchip and a lead frame in a resin-sealed type semiconductor device,characterized in that the adhesive does not dissolve in thesealer-composing resins at the sealer molding temperature, and that itsadhesive strength under shear between a semiconductor chip and a leadframe is 1 N/4 mm² or greater.

The expression “does not dissolve in the sealer-composing resins” usedhere is defined as follows. A glass plate (about 2 mm thick) having a 20μm thick layer of the thermoresistance adhesive is heated to 180° C.,then about 0.1 g of pellets of each sealer-composing resin are placed onthe thermoresistance adhesive layer and allowed to stand at 120 to 200°C. for 2 minutes, after which the molten sealer-composing resin left onthe adhesive is wiped out at the same temperature and the appearance ofthe adhesive layer is visually observed. The above expression applieseither when only a trace of dissolution is admitted at the part of theadhesive layer contacted with the resin pellets or when absolutely nosign of dissolution is admitted. On the other hand, the expression“dissolves in the sealer-composing resins” signifies the case where thethermoresistance adhesive dissolves in the sealer-composing resins toform a molten fluid to create hollows or holes in the adhesive film. Itis desirable that the adhesive does not dissolve in any of the componentresins used, but when the resins are used as a mixture, it is merelyrequired that the adhesive be not dissolved in the mixture per se.

The semiconductor chip/lead frame adhesive strength under shear of thethermoresistance adhesive is measured at 25° C. and a tear-off rate of0.5 mm/sec, using a test piece made by bonding said both members withinterposition of a 20 μm adhesive layer under the conditions of 300° C.,0.2 MPa and 5 seconds.

The “semiconductor chip” generally refers to the one comprising a 670 μmthick silicon wafer having electronic circuits formed thereon or a piececut out therefrom, but the chips contemplated in the present inventionare not limited to this type; the bonded side of the chip may comprise asilicon oxide film or a buffer coat of a heat-resistant resin such aspolyimide resin. The lead frame is usually of the type made of an iron(Fe)/nickel (Ni) alloy (an alloy with Ni content of 42%, hereinafterreferred to as 42 alloy), but are not limited to this type. Formeasurement of adhesive strength under shear, a commercial tester, forexample an automatic adhesion tester Microtester BT-22 mfd. by DageLtd., can be used.

(2) A thermoresistance adhesive set forth in (1) wherein the sealercomprises an epoxy resin or a phenol resin.

(3) A thermoresistance adhesive set forth in (1) or (2) wherein themolding temperature of the sealer is 120 to 200° C.

(4) A thermoresistance adhesive set forth in any one of (1) to (3)wherein the adhesive has a glass transition temperature lower than thetemperature at which a semiconductor chip and a lead frame are bondedafter heat drying.

(5) A thermoresistance adhesive set forth in any one of (1) to (4)wherein the adhesive contains a heat-resistant resin having amide,imide, ester or ether linkage.

(6) A thermoresistance adhesive set forth in any one of (1) to (5)wherein the adhesive is a heat-resistant resin composition obtained byblending 70 to 99.9 parts by weight of a heat-resistant resin having ahydroxyl, amino or carboxyl group in the molecule and 0.1 to 30 parts byweight of a crosslinking agent having functional groups chemicallybondable to the hydroxyl, amino or carboxyl group so that the totalamount of the two will become 100 parts by weight.

(7) A thermoresistance adhesive set forth in (5) or (6) wherein theheat-resistant resin is a polyimide resin, a polyamide-imide resin or aprecursor thereof.

(8) A thermoresistance adhesive set forth in (6) wherein theheat-resistant resin is a polyimide resin or a precursor thereofobtained by reacting an aromatic tetracarboxylic acid dianhydride withan aromatic diamine compound having a diaminohydroxyl compound as anessential component.

(9) A thermoresistance adhesive solution containing an organic solventin addition to the components of the thermoresistance adhesive set forthin any one of (4) to (8).

(10) A thermoresistance adhesive solution set forth in (9) containingfine inorganic or organic particles in an amount ratio of 1 to 70 partsby weight to 30 to 99 parts by weight of the heat-resistant resin sothat the total amount thereof will become 100 parts by weight.

(11) A thermoresistance adhesive solution set forth in (10) wherein thefine organic particles are the fine particles of a heat-resistant resinhaving amide, imide, ester or ether linkage, the average size (diameter)of said particles being 20 μm or less.

(12) A thermoresistance adhesive solution set forth in (10) or (11)wherein before heat drying, the fine organic particles exist as aheterogeneous phase as opposed to the homogeneous phase consisting ofthe heat-resistance resin and the organic solvent, and after heatdrying, there is formed a homogeneous phase containing theheat-resistant resin and the fine organic particles as essentialcomponents.

(13) A thermoresistance adhesive solution set forth in any one of (9) to(12) wherein the organic solvent is a lactone or a carbonate.

(14) A thermoresistance adhesive solution set forth in any one of (9) to(13) having a viscosity of 100 to 400 Pa·s and a thixotropy factor of2.0 to 5.0.

(15) A thermoresistance resin paste comprising (A) a heat-resistantresin having a hydroxyl, amino or carboxyl group in the molecule, (B)fine organic particles, (C) a crosslinking agent having functionalgroups chemically bondable to said hydroxyl, amino or carboxyl group,and (D) a solvent, said materials being blended so that before heatdrying, the fine organic particles (B) exist as a heterogeneous phase asopposed to the homogeneous phase consisting of the heat-resistant resin(A), crosslinking agent (C) and solvent (D), and after heat drying,there is formed a homogeneous phase containing the fine organicparticles (B) and crosslinking agent (C) as essential components.

(16) A thermoresistance resin paste set forth in (15) wherein theheat-resistant resin (A) is a resin whose temperature of 1% weight losson heating is 350° C. or above.

(17) A thermoresistance resin paste set forth in (15) wherein theheat-resistant resin (A) is a polyimide resin having a hydroxyl orcarboxyl group in the molecule.

(18) A thermoresistance resin paste set forth in (17) wherein thepolyimide resin having a hydroxyl group in the molecule is the oneobtained by reacting an aromatic tetracarboxylic acid dianhydride withan aromatic diamine containing a diaminohydroxyl compound as anessential component.

(19) A thermoresistance resin paste set forth in (18) wherein thediaminohydroxyl compound is 2,2-bis(4-hydroxy-3-aminophenyl)propane,2,2-bis(4-hydroxy-3-aminophenyl)hexafluoropropane or3,3′-dihydroxy-4,4′-diaminobiphenyl.

(20) A thermoresistance resin paste set forth in (15) wherein the fineorganic particles (B) are the fine particles of a heat-resistant resinwhose temperature of 1% weight loss on heating is 350° C. or above, theaverage size (diameter) of the said particles being 20 μm or less.

(21) A thermoresistance resin paste set forth in (20) wherein theheat-resistant resin particles are the polyimide resin particles.

(22) A thermoresistance resin paste set forth in (15) wherein thecrosslinking agent (C) is a coupling agent.

(23) A thermoresistance resin paste set forth in (22) wherein thecoupling agent is a silane coupling agent.

(24) A thermoresistance resin paste set forth in (15) wherein thesolvent (D) is a lactone, an ether or a carbonate.

(25) A thermoresistance resin paste set forth in (15) comprising (A) aheat-resistant resin having a hydroxyl, amino or carboxyl group in themolecule, (B) fine organic particles, and (C) a crosslinking agenthaving functional groups chemically bondable to said hydroxyl, amino orcarboxyl group, wherein the amount of (B) is 10 to 300 parts by weightand the amount of (C) is 1 to 30 parts by weight, per 100 parts byweight of (A).

(26) A thermoresistance resin paste set forth in (15) having athixotropy factor of 1.5 or greater and a viscosity of 10 to 500 Pa·s.

(27) A thermoresistance adhesive obtained by drying the thermoresistanceadhesive solution set forth in any one of (9) to (14) or thethermoresistance resin paste set forth in any one of (15) to (26).

(28) A semiconductor chip having a thermoresistance adhesive layerproduced by providing a layer of the thermoresistance adhesive set forthin any one of (1) to (8) and (27) on the circuit forming side of asemiconductor chip.

(29) A lead frame having a thermoresistance adhesive layer produced byproviding a layer of the thermoresistance adhesive set forth in any oneof (1) to (8) and (27) on the semiconductor-mounted side of a leadframe.

(30) A film having a thermoresistance adhesive layer produced byproviding a layer of the thermoresistance adhesive set forth in any oneof (1) to (8) and (27) on one or both sides of a support film.

(31) A semiconductor device in which the plural inner leads of a leadframe are bonded to the circuit-formed side of a semiconductor chip bythe thermoresistance adhesive set forth in any one of (1) to (8) and(27), and the semiconductor chip and the inner leads of the lead frameare electrically connected by wire bonding, said semiconductor chipbeing sealed by a sealer.

(32) A semiconductor in which the plural inner leads of a lead frame arebonded to the circuit forming side of a semiconductor chip having alayer of said thermoresistance adhesive with interposition of a layer ofthe thermoresistance adhesive set forth in any one of (1) to (8) and(27), and the semiconductor chip and the inner leads of the lead frameare electrically connected by wire bonding, said semiconductor chipbeing sealed by a sealer.

(33) A semiconductor device in which the plural inner leads of said leadframe having a thermoresistance adhesive layer are bonded to the circuitforming side of a semiconductor chip through a layer of thethermoresistance adhesive set forth in any one of (1) to (8) and (27),and the semiconductor chip and the inner leads of the lead frame areelectrically connected by wire bonding, said semiconductor chip beingsealed by a sealer.

(34) A semiconductor device in which the plural inner leads of a leadframe are bonded to the circuit forming side of a semiconductor chipwith the inter-position of a film having a layer of the thermoresistanceadhesive set forth in any one of (1) to (8) and (27), and thesemiconductor chip and the inner leads of the lead frame areelectrically connected by wire bonding, said semiconductor chip beingsealed by a sealer.

(35) A process for producing a thermoresistance resin paste whichcomprises mixing (I) a heat-resistant resin A soluble in the solvent of(III) at room temperature and at the heat drying temperature, (II) aheat-resistant resin B insoluble in the solvent of (III) at roomtemperature but soluble at the heat drying temperature, and (III) asolvent, dissolving the said materials by heating, and cooling theresulting solution to have the fine particles of the heat-resistantresin B of (II) deposited and dispersed in the solution of theheat-resistant resin A of (I) and the solvent of (III).

(36) The process for producing a thermoresistance resin paste set forthin (35) wherein the heat-resistant resin A of (I) and the heat-resistantresin B of (II) are an aromatic polyimide resin obtained by reacting anaromatic tetracarboxylic acid dianhydride and an aromatic diamine.

(37) The process for producing a thermoresistance resin paste set forthin (36) wherein the heat-resistant B of (II) is an aromatic polyimideresin obtained by reacting an aromatic tetracarboxylic acid dianhydridecontaining 50 mol % or more of bis(3,4-dicarboxyphenyl)-etherdianhydride with an aromatic diamine containing 50 mol % or more of2,2-bis[4-(4-aminophenoxy)phenyl]propane, and the solvent of (III) isγ-butyrolactone.

(38) The process for producing a thermoresistance resin paste set forthin (36) wherein the fine particles of the heat-resistant resin B of (II)are deposited and dispersed in a solution of the heat-resistant resin Aof (I) and the solvent of (III) so that the maximal size of theparticles will become 10 μm or less.

(39) The process for producing a thermoresistance resin paste set forthin (36) wherein the fine particles of the heat-resistant resin B of (II)are deposited and dispersed in a solution of the heat-resistant resin Aof (I) and the solvent of (III) so that the paste will have a thixotropyfactor of 1.5 or greater.

The thermoresistance adhesive according to the present invention is theone which does not dissolve in the sealer-composing resins at the sealermolding temperature and whose semiconductor chip/lead frame adhesivestrength under shear is 1 N/4 mm² or greater. Such a thermoresistanceadhesive contains a heat-resistant resin. The term “heat-resistant”(resin) used here signifies that the resin has such a degree of heatresistance that it won't dissolve at the sealer molding temperature,preferably such a degree of heat resistance that it won't dissolve atthe heating temperature used for wire bonding. Examples of suchheat-resistant resins include those having amide linkage, imide linkage,ester linkage or ether linkage, specifically polyimide resins,polyamide-imide resins, polyamide resins, polyester resins and polyetherresins. Regarding the polyimide and polyamide resins, it is possible touse polyamide acid, which is the precursor of such resins, and itspartially imidized resins. The thermoresistance adhesive containing sucha heat-resistant resin may be either thermoplastic or thermosetting andis not restricted in type as far as it does not dissolve in thesealer-composing resins at the sealer molding temperature and is capableof heat bonding a semiconductor chip and a lead frame, with itssemiconductor chip/lead frame adhesive strength under shear being 1 N/4mm² or greater.

Polyimide resins can be obtained by reacting aromatic tetracarboxylicacid dianhydrides with aromatic diamine compounds.

Examples of the aromatic tetracarboxylic acid dianhydrides usable forthe said purpose include pyromellitic acid dianhydride,3,3′,4,4′-biphenyl-tetracarboxylic acid dianhydride,2,2′,3,3′-biphenyltetracarboxylic acid dianhydride,2,3,3′,4′-biphenyltetracarboxylic acid dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,2,2-bis(2,3-dicarboxyphenyl)propane dianhydride,1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride,1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride,bis(2,3-dicarboxyphenyl)methane dianhydride,bis(3,4-dicarboxyphenyl)methane dianhydride,bis(3,4-dicarboxyphenyl)sulfone dianhydride,3,4,9,10-perillenetetracarboxylic acid dianhydride,bis(3,4-dicarboxyphenyl)ether dianhydride,benzene-1,2,3,4-tetracarboxylic acid dianhydride,3,4,3′,4′-benzophenonetetracarboxylic acid dianhydride,2,3,2′,3′-benzophenonetetracarboxylic acid dianhydride,2,3,2′,3′-benzophenonetetracarboxylic acid dianhydride,2,3,3′,4′-benzophenonetetracarboxylic acid dianhydride,1,2,5,6-naphthalenetetracarboxylic acid dianhydride,2,3,6,7-naphthalenetetracarboxylic acid dianhydride,1,2,4,5-naphthalenetetracarboxylic acid dianhydride,1,4,5,8-naphthalenetetracarboxylic acid dianhydride,2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride,2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride,2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride,phenanthrene-1,8,9,10-tetracarboxylic acid dianhydride,bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride,bis(3,4-dicarboxyphenyl)methylphenylsilane dianhydride,bis(3,4-dicarboxyphenyl)diphenylsilane dianhydride,1,4-bis(3,4-dicarboxyphenyldimethylsilyl)benzene dianhydride,1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldicyclohexanedianhydride, p-phenylenebis(trimellitic acid monoester dianhydride),2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride,1,4-bis(2-hydroxyhexafluoroisopropyl)benzenebis(trimellitate anhydride),1,3-bis(2-hydroxyhexafluoroisopropyl)benzenebis(trimellitate anhydride),1,2-(ethylene)bis(trimellitate anhydride),1,3-(trimethylene)bis(trimellitate anhydride),1,4-(tetramethylene)bis(trimellitate anhydride),1,5-(pentamethylene)bis(trimellitate anhydride),1,6-(hexamethylene)bis(trimellitate anhydride),1,7-(heptamethylene)bis(trimellitate anhydride),1,8-(octamethylene)bis(trimellitate anhydride),1,9-(nonamethylene)bis(trimellitate anhydride),1,10-(decamethylene)bis(trimellitate anhydride),1,12-(dodecamethylene)bis(trimellitate anhydride),1,16-(hexadecamethylene)bis(trimellitate anhydride), and1,18-(octadecamethylene)bis(trimellitate anhydride). These compounds maybe used singly or as a mixture of two or more.

For the said aromatic tetracarboxylic acid dianhydrides, it is possibleto use where necessary the tetracarboxylic acid dianhydrides other thanthe said aromatic tetracarboxylic acid dianhydrides within limits notexceeding 50 mol % of the aromatic tetracarboxylic acid dianhydride.Examples of such tetracarboxylic acid dianhydrides includeethylenetetracarboxylic acid dianhydride, 1,2,3,4-butanetetracarboxylicacid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride,thiophene-2,3,4,5-tetracarboxylic acid dianhydride,decahydronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride,4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylicacid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride,pyrrolidine-2,3,4,5-tetracarboxylic acid dianhydride,1,2,3,4-cyclobutanetetracarboxylic acid dianhydride,bis(exo-bicyclo[2,2,1]heptane-2,3-dicarboxylic acid anhydride)sulfone,bicyclo-(2,2,2)-octo(7)-ene-2,3,5,6-tetracarboxylic acid dianhydride,5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylicacid anhydride, and tetrahydrofuran-2,3,4,5-tetracarboxylic aciddianhydride.

Examples of the aromatic diamine compounds include o-phenylenediamine,m-phenylenediamine, p-phenylenediamine, 3,3′-diaminodiphenyl ether,4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane,4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenyldifluoromethane,4,4′-diaminodiphenyldifluoromethane, 3,3′-diaminodiphenylsulfone,3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone,3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide,4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl ketone,3,4′-diaminodiphenyl ketone, 4,4′-diaminodiphenyl ketone,2,2-bis(3-aminophenyl)propane, 2,2-(3,4′-diaminodiphenyl)propane,2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)hexafluoropropane,2,2-(3,4′-diaminodiphenyl)hexafluoropropane,2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene,1,4-bis(4-aminophenoxy)benzene,3,3′-[1,4-phenylenebis(1-methylethylidene)]bisaniline,3,4′-[1,4-phenylenebis(1-methylethylidene)]bisaniline,4,4′-[1,4-phenylenebis(2-methylethylidene)]bisaniline,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane,bis[4-(3-aminophenoxy)phenyl]sulfide,bis[4-(4-aminophenoxy)phenyl]sulfide,bis[4-(3-aminophenoxy)phenyl]sulfone, andbis4-(4-aminophenoxy)phenyl]sulfone. These compounds may be used eithersingly or as a mixture of two or more.

For these aromatic diamine compounds, it is possible to use wherenecessary the diamine compounds other than the said aromatic diaminecompounds within limits not exceeding 50 mol % of the aromatic diaminecompound. Examples of such diamine compounds include 1,2-diaminoethane,1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane,1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane,1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane,1,3-bis(3-aminopropyl)tetramethyldisiloxane, and1,3-bis(3-aminopropyl)tetramethylpolysiloxane.

In the present invention, it is preferable in view of film properties toreact equimolar amounts of an aromatic tetracarboxylic acid dianhydrideand an aromatic diamine compound.

Reaction of an aromatic tetracarboxylic acid dianhydride and an aromaticdiamine compound is carried out in an organic solvent. The organicsolvents usable for the reaction include nitrogeneous compounds such asN-methylpyrrolidone, dimethylacetamide, dimethyl-formamide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, and1,3-dimethyl-2-imidazoridinone; sulfur compounds such as sulforan anddimethyl sulfoxide; lactones such as γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-heptalactone, α-acetyl-γ-butyrolactone andε-caprolactone; ethers such as dioxane, 1,2-dimethoxyethane, diethyleneglycol dimethyl (or diethyl, dipropyl or dibutyl) ether, triethyleneglycol (or diethyl, dipropyl or dibutyl) ether, and tetraethylene glycoldimethyl (or diethyl, dipropyl or dibutyl) ether; ketones such as methylethyl ketone, methyl isobutyl ketone, cyclohexanone and acetophenone;alcohols such as butanol, octyl alcohol, ethylene glycol; glycerin,diethylene glycol monomethyl (or monoethyl) ether, triethylene glycolmonomethyl (or monoethyl) ether, and tetraethylene glycol monomethyl (ormonoethyl) ether; phenols such as phenol, cresol and xylenol; esterssuch as ethyl acetate, butyl acetate, ethyl cellosolve acetate and butylcellosolve acetate; hydrocarbons such as toluene, xylene, diethylbenzeneand cyclohexane; and halogenated hydrocarbons such as trichloroethane,tetrachloroethane and monochlorobenzene. These solvents may be usedeither singly or as a mixture of two or more. Lactones, ethers andketones are preferred in view of solubility, hygroscopicity,low-temperature setting and environmental safety.

The reaction is carried out at 80° C., preferably at 0 to 50° C. As thereaction proceeds, the reaction solution is gradually thickened, andpolyamide acid, which is the precursor of polyimide resin, is formed.This polyamide acid may be partially imidized. The partially imidizedversion is also included in the category of polyimide resin precursor inthe present invention.

Polyimide resin can be obtained from dehydration ring closure of thesaid reaction product (polyamide acid). Dehydration ring closure can beeffected by such method as heat treatment at 120-250° C. (thermalimidization) or using a dehydrating agent (chemical imidization). In thecase of the heat treatment at 120-250° C., it is preferably carried outwhile removing water generated by the dehydration reaction out of thesystem. In this case, water may be removed as an azeotrope with asolvent such as benzene, toluene or xylene.

In case dehydration ring closure is effected by using a dehydratingagent, it is preferable to use an acid anhydride such as aceticanhydride, propionic anhydride or benzoic anhydride, a carbodiimidecompound such as dicyclohexylcarbodiimide, or the like as dehydratingagent. In this case, if necessary, a dehydration catalyst such aspyridine, isoquinoline, trimethylamine, aminopyridine or imidazole maybe used. The dehydrating agent or dehydration catalyst is preferablyused in an amount of 1 to 8 moles per mole of the aromatictetracarboxylic acid dianhydride.

The polyamide-imide resin or its precursor used in the present inventioncan be produced by using a trivalent tricarboxylic acid anhydride or aderivative thereof such as trimellitic acid anhydride or its derivative(such as chloride of trimellitic acid anhydride) in place of thearomatic tetracarboxylic acid dianhydride in the production of the saidpolyimide or its precursor. It is also possible to produce the saidpolyimide resin or its precursor by using, in place of the aromaticdiamine compound or other diamine compound, a diisocyanate compound inwhich the residues other than amino group correspond to the said diaminecompound. The diisocyanate compounds usable here include those obtainedby reacting the said aromatic diamine compounds or other diaminecompounds with phosgene or thionyl chloride.

The polyamide resin used in the present invention can be produced byreacting an aromatic dicarboxylic acid such as terephthalic acid,isophthalic acid and phthalic acid, or a derivative thereof such asdichloride or anhydride of said acids, with an aromatic diamine compoundor other diamine compound such as mentioned above.

The polyester resins usable in the present invention include thoseobtainable by reacting the said aromatic dicarboxylic acids such asterephthalic acid, isophthalic acid and phthalic acid, or theirderivatives such as dichlorides and acid anhydrides, with an aromaticdiol compound such as 1,4-dihydroxybenzene, bisphenol F, bisphenol A or4,4′-dihydroxybiphenyl.

The polyamide-imide resin used in the present invention is preferablythe one obtained by reacting an aromatic tetracarboxylic aciddianhydride with an aromatic diamine compound containing isophthalicacid dihydrazide as essential component. As the aromatic tetracarboxylicacid dianhydride and aromatic diamine amound, those mentioned above canbe used. The molar ratio of isophthalic acid dihydrazide in the aromaticdiamine compound is preferably adjusted to be 1 to 100%. If the molarratio is less than 1%, resistance to dissolution in the sealer-composingresins tends to reduce, while a high content of isophthalic aciddihydrazide tends to lower moisture vapor resistance of the adhesivelayer. The preferred molar ratio of isophthalic acid dihydrazide istherefore 10 to 80%, more preferably 20 to 70%. This polyamide-imideresin can be synthesized by using the same aromatic tetracarboxylic aciddianhydride/aromatic diamine compound ratio, the same organic solventand the same synthetic process as employed for the synthesis of the saidpolyimide resin.

The thermoresistance adhesive according to the present invention may beused in the form a solution by dissolving the adhesive in an organicsolvent, and this adhesive solution may be applied to one or both of theadherends, such as a semiconductor chip and a lead frame, so as to forman adhesive layer in advance. Also, the adhesive may be initially workedinto a film product such as adhesive tape, adhesive film or adhesivesheet and used as such product. Such adhesive tape, adhesive film oradhesive sheet can be obtained, for example, by applying or casting thethermoresistance adhesive solution on a substrate such as a glass plateor a stainless plate and, after drying, separating the coating to obtainan adhesive tape, adhesive film or adhesive sheet made of the saidadhesive alone, or by applying the thermoresistance adhesive solution onboth sides of a substrate such as a plastic film and drying to form anadhesive layer thereon to obtain an adhesive tape, adhesive film oradhesive sheet. Also, the thermoresistance adhesive solution may beimpregnated in a thin fabric mat made of fiber with high heat resistancesuch as glass fiber and dried to make a fiber-reinforced adhesive sheet.

Especially when applying the thermoresistance adhesive solution to suchadherends as semiconductor chip and lead frame, it is preferable toafford appropriate thixotropic properties to the solution. This provesto be advantageous for screen printing in particular.

The thermoresistance adhesive solutions to which appropriate thixotropicproperties have been afforded, namely the thixotropic thermoresistanceadhesives include the thermoresistance resin pastes prepared bycontaining the fine inorganic or organic particles in the saidthermoresistance adhesive solutions. Incorporation of the inorganic ororganic particles makes it possible to afford the thixotropic propertiesrequired for screen printing. Such inorganic or organic particles arepreferably blended in an amount of 1 to 70 parts by weight to 30 to 99parts by weight of the heat-resistant resin so that the total amount ofthe two materials will become 100 parts by weight. When the amount ofthe inorganic or organic particles blended is less than 1 part byweight, it may not be possible to provide the thixotropic propertiesrequired for screen printing, making it difficult to obtain the desiredresolving potency. Presence of the inorganic or organic particles inexcess of 70 parts by weight tends to deteriorate transfer performanceand processability in screen printing. More preferably, the saidinorganic or organic particles are used in an amount of 50 to 5 parts byweight to 50 to 95 parts by weight of the heat-resistant resin so thatthe total of the two materials will become 100 parts by weight.

The inorganic particles usable in the present invention include theinsulating inorganic fine particles of such materials as silica,alumina, titania, tantalum oxide, zirconia, silicon nitride, bariumtitanate, barium carbonate, lead titanate, lead titanozirconate,lanthanum lead titano-zirconate, gallium oxide, spinnel, mullite,cordierite, talc, aluminum titanate, yttria-containing zirconia, bariumsulfate, and barium silicate.

The heat-resistant resin constituting the main component of thethermoresistance resin paste is the one which is soluble in the organicsolvent used for forming the thermoresistance adhesive solution, whereasthe organic particles used in this invention are those which areinsoluble in the said organic solvent before heat drying.

As the organic particles, it is preferable to use the fine particles ofa heat-resistant resin having amide, imide, ester or ether linkage.Preferred examples of such heat-resistant resins are polyimide resinsand their precursors, polyamide-imide resins and their precursors, andpolyamide resins, in view of heat resistance and mechanical properties.

The said polyimide resins and their precursors, polyamide-imide resinsand their precursors, and polyamide resins, can be selected from thoseexemplified above.

These fine particles of heat-resistant resins are selected from thosewhich are insoluble in the organic solvent in the thermoresistanceadhesive solution before heat drying.

As means for forming the fine particles, it is possible to employvarious methods which include, for example, non-aqueous dispersionpolymerization method (JP-B 60-48531 and JP-A 59-230018), precipitationpolymerization method (JP-A 59-108030), method in which the powderrecovered from the resin solution is mechanically ground, method inwhich the resin solution is added to a poor solvent and worked into fineparticles under high shearing force, method in which the atomized resinsolution is dried to form the fine particles, and method in which aresin having temperature dependency of solubility in the solvent or thesolvent in the resin solution is formed into fine particles byprecipitation means.

The thermal decomposition temperature of the fine organic particles ispreferably not lower than 250° C., and it is especially preferable touse the heat-resistant resin particles whose thermal decompositiontemperature is not lower than 350° C.

Two or more types of inorganic and organic particles may be used asrequired. It is also possible to use a mixture of inorganic and organicparticles.

Both inorganic and organic particles are preferably of an average sizeof 40 μm or less. It is more preferable to use the fine particles of aheat-resistant resin having amide, imide, ester or ether linkage with anaverage particle size of 20 μm or less, preferably 0.1 to 10 μm, whichcan minimize the damage to the semiconductor chip when applying thethixotropic thermoresistance adhesive or thermoresistance resin paste toscreen printing, and which can also reduce the ionic contaminantconcentration.

As the thermoresistance resin paste, it is preferable to use the oneprepared by blending the particles in such a manner that the organicparticles will exist as a heterogeneous phase as opposed to thehomogeneous layer containing a heat-resistant resin and an organicsolvent before heat drying, while a homogeneous phase containing theheat-resistant resin and organic solvent as essential components will beformed after heat drying. As mentioned above, the heat-resistant resinconstituting the main component of the thermoresistance resin paste isthe one which is soluble in the organic solvent used for thethermoresistance adhesive solution, while the organic particles arethose which are insoluble in said organic solvent before heat drying,but it is desirable that both of them have the nature that they dissolvein said organic solvent at the temperature used for heat drying. “Heatdrying” referred to in this invention means drying conducted whenforming an adhesive layer on the adherend, and drying performed inmaking of said adhesive tape, adhesive film or adhesive sheet by heatingat 50 to 350° C. In some cases, the thermoresistance resin paste may beapplied to the adherend to effect adhesion simultaneously with drying.

In order that a homogeneous phase containing the heat-resistant resinand fine organic particles as essential components may be formed afterheat drying, it is desirable that the heat-resistant resin and organicparticles used are compatible with each other. Specifically, it ispreferable to use a combination of heat-resistant resin and organicparticles in which the difference in solubility parameter between theheat-resistant resin and the organic particles is 2.0 or less, morepreferably 1.5 or less. The “solubility parameter” referred to herein isthe value (unit: (MJ/m3)1/2) determined according to the Fedors methoddescribed in Polym. Eng. Sci., Vol. 14, pp. 147-154. The heat-resistantresin compositions using such fine organic particles are disclosed in,for instance, JP-A 2-289646, JP-A 4-248871 and JP-A 4-85379, and thesecompositions can be used in the present invention. Said heat-resistantresins can be used as the organic particles, but as mentioned before,these organic particles must be of the type which, before heat drying,is insoluble in the organic solvent used for forming a thermoresistanceadhesive solution. The thermoresistance resin paste using such organicparticles, as compared with a thermoresistance resin paste using theinorganic and organic particles insoluble in the organic solvent both atroom temperature and at heat drying temperature, is capable of forming auniform and thick film free of such defects as pinholes or voids, andalso makes it possible to form a dry film with excellent mechanicalstrength and humidity resistance. The thermoresistance adhesive of theabove formulation—in which the organic particles exist as aheterogeneous phase as opposed to the homogeneous phase containing aheat resistant resin and organic particles before heat drying, and ahomogeneous phase containing a heat-resistant resin or organic particlesand a crosslinking agent as essential components is formed after heatdrying—is particularly preferred in terms of adhesion of a chip and alead frame, adhesiveness to the sealer, and resistance to packagecracking in solder reflowing. The crosslinking agent is preferably ofthe type which forms a homogeneous phase with the heat-resistant resinand solvent before heat drying. The crosslinking agent may be reactedwith the heat-resistant resin before heat drying, but preferably it isreacted with the heat-resistant resin in the course of heat drying.

Any of the said homogeneous phases may contain the organic solvent whichremains after heat drying.

As the organic solvent for the thermoresistance adhesive solution orthermoresistance resin paste according to this invention, it is possibleto use, for instance, the solvents described in Solvent Handbook,Kodansha, 1976, pp. 143-852. Examples of such solvents includenitrogenous compounds such as N-methylpyrrolidone, dimethylacetamide,dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone,and 1,3-dimethyl-2-imidazolidinone; sulfur compounds such as sulforanand dimethyl sulfoxide; lactones such as γ-butyrolactone,γ-valerolactone, γ-caprolactone, γ-heptalactone, α-acetyl-,γ-butyrolactone and ε-caprolactone; ethers such as dioxane,1,2-dimethoxyethane, diethylene glycol dimethyl (or diethyl, dipropyl ordibutyl) ether, triethylene glycol dimethyl (or diethyl, dipropyl ordibutyl) ether, and tetraethylene glycol dimethyl (or diethyl, dipropylor dibutyl) ether; ketones such as methyl ethyl ketone, methyl isobutylketone, cyclohexanone and acetophenone; alcohols such as butanol, octylalcohol, ethylene glycol, glycerin, diethylene glycol monomethyl (ormonoethyl) ether, triethylene glycol monomethyl (or monoethyl) ether,and tetraethylene glycol monomethyl(or monoethyl) ether; phenols such asphenol, cresol and xylenol; esters such as ethyl acetate, butyl acetate,ethyl cellosolve acetate and butyl cellosolve acetate; hydrocarbons suchas toluene, xylene, diethylbenzene and cyclohexane; halogenatedhydrocarbons such as trichloroethane, tetrachloroethane andmonochlorobenzene; and carbonates such as ethylene carbonate andpropylene carbonate.

The boiling point of the solvent should be 100° C. or higher, preferably150 to 300° C., in view of the available period of the paste for screenprinting. Also, considering hygroscopic stability and volatility of thepaste, it is preferable to use non-nitrogenous solvents, for example,lactones such as γ-butyrolactone, γ-valerolactone, γ-caprolactone,γ-heptalactone, α-acetyl-γ-butyrolactone and ε-caprolactone, andcarbonates such as ethylene carbonate and propylene carbonate.

For dispersing the inorganic or organic particles in the heat-resistantresin, the methods commonly used in coating industry, such as rollmilling and ball milling, can be employed; any method can be used as faras it is capable of effecting desired dispersion. A dispersion methodwhich requires no mixing operation for directly precipitating and makingfiner the organic particles in the heat-resistant resin solution isespecially preferred as this method can reduce the ionic contaminantconcentration in the dispersion step and also allows a significant costreduction.

As the heat-resistant resin, it is possible to use the resins havingfunctional groups such as hydroxyl group, amino group and carboxylgroup. These groups may exist at the terminal of the resin molecule inthe heat-resistant resin, but it is preferable to use a resin in whichthe said groups exist in the molecule, not at the terminal. In case theresin has functional groups such as mentioned above, it is preferable touse a crosslinking agent having functional groups which are reactivewith the above-said functional groups.

As the thermoresistance resin paste, it is preferable to use the onespecified below: a thermoresistance resin paste comprising (A) aheat-resistant resin having functional groups such as hydroxyl group,amino group or carboxyl group in the molecule, (B) fine organicparticles, (C) a crosslinking agent having functional groups which arechemically bondable to the said functional groups such as hydroxylgroup, amino group or carboxyl group, and (D) a solvent, these materialsbeing blended in such a manner that the organic particles will exist asa heterogeneous phase as opposed to the homogeneous phase containing theheat-resistant resin (A), crosslinking agent.(C) and solvent (D) beforeheat drying, and a homogeneous phase containing the heat-resistant resin(A), organic particles (B) and crosslinking agent (C) as essentialcomponents will be formed after heat drying.

As the crosslinking agent, the compounds having one or more of epoxygroup, hydroxyl group, amino group, carboxyl group, methylol group,maleimide group, oxazoline group, vinyl group, methacryloyl group,methoxysilane group and ethoxysilane group, at least two of any group,in the molecule can be used. The ratio of the heat-resistant resin tothe crosslinking agent in the composition is preferably 70-99.9 to0.1-30 (in parts by weight) with the total of the two being 100 parts byweight. When the ratio of the crosslinking agent is less than 1 part byweight, the degree of crosslinking of the heat-resistant resin isinsufficient, making the said resin liable to dissolve in the sealercomposing resins at the sealer molding temperature and increasing therisk of package cracking in solder reflowing. On the other hand, whenthe ratio of the crosslinking agent exceeds 30 parts by weight, thedegree of crosslinking of the heat-resistant resin becomes excessive toreduce heat bonding force to the semiconductor chip or lead frame,resulting in a decreased adhesive strength under shear. It is thuspreferable to use a crosslinking agent which can provide a moderatedegree of crosslinking. The type of the crosslinking agent to be used inthe present invention is not specified, but the coupling agents arepreferred. The crosslinking agent is preferably blended in a ratio ofcrosslinking agent to heat-resistant resin of 0.5-25 to 75-99.5 (inparts by weight) with the total of the two being 100 parts by weight.

As the heat-resistant resin having said functional groups, it ispreferred to use the resins having hydroxyl, amino or carboxyl group,and as the crosslinking agent, those having the functional groupschemically bondable to the hydroxyl, amino or carboxyl group arepreferably used. As the crosslinking agent having the functional groupschemically bondable to the hydroxyl, amino or carboxyl group, it ispreferable to use the one having two or more functional groups in themolecule, at least one of such functional groups being reacted with thesaid heat-resistant resin having hydroxyl, amino or hydroxyl group whilethe other functional group(s) is reacted with the heat-resistant resinhaving hydroxyl or carboxyl group in the molecule or reacted with eachother. The crosslinking agent used in the present invention is notsubject to any specific restrictions regarding molecular structure,molecular weight, etc., as far as it has at least two functional groups.Typical examples of the functional groups which react with hydroxylgroup are epoxy group, isocyanate group and methylol group. Examples ofthe functional groups which react with carboxyl group are epoxy group,amino group, vinyl group and oxazoline group. Examples of the functionalgroups which react with each other are methoxysilane group andethoxysilane group. The silane coupling agents which can afford amoderately crosslinked structure to the dried product of thethermoresistance resin paste and can also provide storage stability tothe paste are preferably used as crosslinking agent. Such couplingagents include, for example, silane coupling agents, titanate-basedcoupling agents and aluminum-based coupling agents. The silane couplingagents are the most preferred.

The heat-resistant resin having hydroxyl group in the molecule can beproduced by using a diaminohydroxyl compound having hydroxyl group as apart of the diamine moiety in the synthesis of said polyimide resins andtheir precursor, polyamide-imide resins and their precursor, andpolyamide resins.

Examples of the diaminohydroxyl compounds usable in the presentinvention include the following: 1,2-diamino-4-hydroxybenzene,1,3-diamino-5-9hydroxybenzene, 1,3-diamino-4-hydroxybenzene,1,4-diamino-6-hydroxybenzene, 1,5-diamino-6-hydroxybenzene,1,3-diamino-4,6-dihydroxybenzene, 1,2-diamino-3,5-dihydroxybenzene,4-(3,5-diaminophenoxy)phenyl, 3-(3,5-diaminophenoxy)phenol,2-(3,5-diaminophenoxy)phenol, 3,3′-dihydroxy-4,4′-diaminobiphenyl,3,3′-diamino-4,4′-dihydroxybiphenyl,2,2-bis(4-hydroxy-3-aminophenyl)propane,2,2-bis(4-hydroxy-3-aminophenyl)hexafluoropropane,bis(4-hydroxy-3-aminophenyl) ketone,2,2-bis(4-hydroxy-3-aminophenyl)sulfide,2,2-bis(4-hydroxy-3-aminophenyl)ether,2,2-bis(4-hydroxy-3-aminophenyl)sulfone,2,2-bis(4-hydroxy-3-aminophenyl)methane,4-[(2,4-diamino-5-pyrimidinyl)methyl]phenol,p-(3,6-diamino-s-triazine-2-yl)phenol,2,2-bis(4-hydroxy-3-aminophenyl)difluoromethane,2,2-bis(4-amino-3-hydroxyphenyl)propane,2,2-bis(4-amino-3-hydroxyphenyl)hexafluoropropane,bis(4-amino-3-hydroxyphenyl)ketone, 2,2-bis(4-amino-3-hydroxyphenyl)sulfide, 2,2-bis(4-amino-3-hydroxyphenyl)ether,2,2-bis(4-amino-3-hydroxyphenyl)sulfone,2,2-bis(4-amino-3-hydroxyphenyl)methane,2,2-bis(4-amino-3-hydroxyphenyl)difluoromethane, and the compoundsrepresented by the following formulae:

Of these compounds, 2,2-bis(4-hydroxy-3-aminophenyl)propane,2,2-bis(4-hydroxy-3-aminophenyl)hexafluoropropane and3,3′-dihydroxy-4,4′-diaminobiphenyl are preferred as they are active inelevating solubility and hydroxyl group concentration and economicallyadvantageous.

The molar ratio of the diaminohydroxyl compound in the aromatic diaminecompound is preferably adjusted to be 1 to 100 mol %. When its ratio isless than 1 mol %, compound resistance to dissolving in the sealercomposing resins tends to lower, while a too high content of thediaminohydroxyl compound tends to increase moisture absorption of thedry film. Thus, the preferred ratio of the diaminohydroxl compound is 5to 80 mol %, more preferably 10 to 50 mol %.

The heat-resistant resin having carboxyl group in the molecule can beproduced by using a diamine compound having carboxyl group as a part ofthe diamine moiety in the synthesis of said polyimide resins or theirprecursor, polyamide-imide resins or their precursor, and polyamideresins.

It is preferable to use the diamine compounds having at least onecarboxyl group in the molecule. Examples of such diamine compoundsinclude 1,2-diamino-4-carboxybenzene, 1,3-diamino-5-carboxybenzene,1,3-diamino-4-carboxybenzene, 1,4-diamino-6-carboxybenzene,1,5-diamino-6-carboxybenzene, 1,3-diamino-4,6-dicarboxybenzene,1,2-diamino-3,5-dicarboxybenzene, 4-(3,5-diaminophenoxy)benzoic acid,3-(3,5-diaminophenoxy)benzoic acid, 2-(3,5-daminophenoxy) benzoic acid,3,3′-dicarboxy-4,4′-diaminobiphenyl,3,3′-dicarboxy-4,4′-dicarboxybiphenyl,2,2-bis(4-carboxy-3-aminophenyl)propane,2,2-bis(4-carboxy-3-aminophenyl)hexafluoropropane,bis(4-carboxy-3-aminophenyl) ketone, 2,2-bis(4-carboxy-3-aminophenyl)sulfide, 2,2-bis(4-carboxy-3-aminophenyl)ether,2,2-bis(4-carboxy-3-aminophenyl)sulfone,2,2-bis(4-carboxy-3-aminophenyl)methane,4-[(2,4-diamino-5-pyrimidinyl)methyl]benzoic acid,p-(3,6-diamino-s-triazine-2-yl)benzoic acid,2,2-bis(4-carboxy-3-aminophenyl)difluoromethane,2,2-bis(4-amino-3-carboxyphenyl)propane,2,2-bis(4-amino-3-carboxyphenyl)hexafluoropropane,bis(4-amino-3-carboxyphenyl) ketone, 2,2-bis(4-amino-3-carboxyphenyl)sulfide, 2,2-bis(4-amino-3-carboxyphenyl)ether,2,2-bis(4-amino-3-carboxyphenyl)sulfone,2,2-bis(4-amino-3-carboxyphenyl)methane, and2,2-bis(4-amino-3-carboxyphenyl)difluoromethane. Of these compounds,1,3-diamino-5-carboxybenzene is preferred because of excellent heatresistance, flexibility and economy. An aromatic tetracarboxylic aciddianhydride and an aromatic diamine compound containing a diaminecompound having carboxyl group as essential component are preferablyreacted in substantially equimolar quantities for providing the bestfilm properties. The ratio of the diamine compound having carboxyl groupin the aromatic diamine compound is preferably adjusted to be 1 to 100mol %. When its ratio is less than 1 mol %, the degree of crosslinkingof the dry film tends to become insufficient, resulting in loweredresistance to dissolving in the sealer composing resins and reducedsolder reflowing efficiency. A high content of the diamine compoundhaving carboxyl group tends to reduce moisture resistance of the dryfilm. Thus, the preferred ratio of the diamine compound is 5 to 80 mol%, more preferably 10 to 50 mol %.

The heat-resistant resin having amino group in the molecule can beproduced by using a triamino compound and a tetraamino compound as apart of the diamine moiety in the synthesis of said polyimide resins ortheir precursor, polyamide-imide resins or their precursor, andpolyamide resins.

Examples of the triamino compounds include 1,3,5-triaminobenzene,3,4,4′-triaminobiphenyl, 3,5,4′-triaminobiphenyl,3,4,4′-triaminodiphenyl ether, and 3,5,4′-triaminodiphenyl ether.

Examples of the tetraamino compounds include3,3′,4,4′-tetraaminobiphenyl and 3,3′,4,4′-tetraaminodiphenyl ether.

The total amount of the triamino compound and tetraamino compound in thewhole amine moiety is preferably adjusted so that their ratio to thediamino compound will be 1-25 to 99-75 in mol %. When the ratio of thetriamino and tetraamino compounds is less than 1 mol %, the degree ofcrosslinking of the dry film tends to become too low, and alsoresistance to dissolution in the sealer composing resins and solderreflowing efficiency tend to lower. When the ratio exceeds 25 mol %,gelation tends to take place in the resin synthesis. As means forcontrolling this gelation, it is recommended to use the acid componentin an amount of 0.5 to 1.0 mole, preferably 0.8 to 0.98 mole in view offilm strength, per mole of the amine component.

A polyimide resin having carboxyl or amino group or its precursor can beobtained by reacting a tetracarboxylic acid anhydride and a diaminecompound. It is possible to use a polyimide resin having carboxyl oramino group only at the terminal of the molecule. The amount of thecarboxyl group and amino group can be adjusted by controlling the mixingratios of said materials.

The coupling agent used in the present invention has at least twofunctional groups in the molecule, at least one of such functionalgroups being reacted with a polyimide resin having hydroxyl, amino orcarboxyl group in the molecule while the other functional group(s) isrequired to react with polyimide resin having hydroxyl, amino orcarboxyl group in the molecular backbone, polyamide-imide resin, theirprecursors, or polyamide resin, or react with each other. These couplingagents are not subject to any specific regulations regarding molecularstructure, molecular weight, etc., as far as they have two or morefunctional groups. The described type of coupling agent include, forinstance, silane coupling agents, titanate coupling agents andaluminum-based coupling agents. The functional groups reacted with saidpolyimide resin having hydroxyl, amino or carboxyl group in themolecular backbone include epoxy group, amino group, vinyl group andmethacryloyl group. Methoxy group and ethoxy group are the typicalexamples of the functional groups which are self-reacted with thefunctional group in the coupling agent.

The preferred type of the coupling agent for use in the presentinvention is the silane coupling agents, the examples of which includeγ-(2-aminoethyl)aminopropyltrimethoxysilane,γ-(2-aminoethyl)aminopropylmethyldimethoxysilane,γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane,γ-mercaptopropyltrimethoxysilane, vinyltriacetoxysilane,γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane,γ-mercaptopropylmethyldimethoxysilane,γ-glycidoxypropylmethyldimethoxysilane, γ-ureidopropyltriethoxysilane,and γ-methacryloxypropylmethylenedimethoxysilane.

It is preferable to use a silane coupling agent having epoxy group andmethoxysilane group in the molecule, especiallyγ-glycidoxypropyltrimethoxysilane, with the polyimide resin,polyamide-imide resin, their precursor or polyamide resin havinghydroxyl, amino or carboxyl group in the molecule. The thermoresistanceadhesive obtained by heat drying a heat-resistant resin compositioncontaining such a coupling agent has a moderately crosslinked structure,so that it does not dissolve in the sealer composing resins at thesealer molding temperature and is capable of providing strong adhesion(especially heat bonding) to the semiconductor chip or lead frame.

The above explanation of the thermoresistance adhesive can be applied tothe organic particles (B) in the thermoresistance resin paste. Thefollowing is a supplementary explanation on the organic particles.

The heat-resistant resin used in said resin paste is of the type whichis soluble in the organic a solvent employed, but the organic particlesare the ones which are insoluble in the organic solvent used. It is,however, desirable that both of them have the nature that they dissolvein the respective organic solvents at the temperature used for heatdrying.

The organic particles (B) are used for affording thixotropic propertiesto the paste. The average size of these organic particles is preferably20 μm or less in view of compatibility with the heat-resistant resin orthe reaction product thereof with a crosslinking agent, solubility inthe solvent and printability. These organic particles are alsopreferably the fine particles of a heat-resistant resin whosetemperature of 1% weight loss on heating is 250° C. or higher as suchparticles are helpful to suppress outgassing in the heat treatments oroperations at high temperatures, for example, wire bonding. The averagesize of the organic particles is more preferably 0.1 to 10 μm,especially 5 μm or less. Also, the organic particles are more preferablythe fine particles of a heat-resistant resin whose temperature of 1%weight loss on heating is 350° C. or above.

The organic particles (B) are preferably the fine particles of aheat-resistant resin having amide, imide, ester or ether linkage. Such aheat-resistant resin is preferably a polyimide resin or its precursor, apolyamide-imide resin or its precursor or a polyamide resin in view ofheat resistance and mechanical properties.

The material of the organic particles (B) may be selected from theabove-mentioned polyimide resin or its precursor, polyamide-imide resinor its precursor, and polyamide resin having hydroxyl, amino or carboxylgroup, but in these resins, it is not always necessary to contain adiamine compound such as diaminohydroxyl compound, triamino compound,tetraamino compound or diaminocarboxyl compound as essential component.

These fine particles of a heat-resistant resin also need to meet therequirement that they are insoluble in the organic solvent for thethermoresistance resin paste in the present invention before heatdrying. Regarding the organic solvent used for the thermoresistanceresin paste in the present invention, the explanation given before withreference to the thermoresistance adhesive solution can be applied.

The combinations of heat-resistant resin composing the organic particlesand organic solvent in the thermoresistance resin paste of the presentinvention are exemplified in Table 1. These are but mere examples of theembodiments of the present invention and never restrictive to the scopeof the invention. It is also desirable that the heat-resistant resin (A)and the organic particles (B) used in the present invention arecompatible with each other. Specifically, there is preferably used aresin (A)/organic particle (B) combination in which the difference insolubility parameter between (A) and (B) is 2.0 or less, more preferably1.5 or less. The “solubility parameter” referred to herein is the value[unit: (MJ/m3)1/2] determined according to the Fedors method describedin Polym. Eng. Sci., Vol. 14, pp. 147-154.

TABLE 1 Organic particles X in formula (1) Y in formula (1) Solvent —O—

γ-butyrolactone

γ-valerolactone —CO—

γ-valerolactone

γ-caprolactone —O—

γ-caprolactone —CO— ″ γ-caprolactone None/—O— = ″ γ-caprolactone 1/1(molar ratio) —O—

γ-caprolactone

Propylene carbonate = 0.9/0.1 (molar ratio)

In the thermoresistance resin paste of the present invention, the ratiosof (A) the heat-resistant resin having functional groups such ashydroxyl, amino and carboxyl groups, (B) the fine organic particles, and(C) the crosslinking agent having functional groups chemically bondableto the above-said functional groups such as hydroxyl, amino and carboxylgroups, are as follows: To 100 parts by weight of (A), (B) is 10 to 300parts by weight and (C) is 1 to 30 parts by weight, preferably (B) is 20to 300 parts by weight and (C) is 5 to 30 parts by weight, morepreferably (B) is 20 to 200 parts by weight and (C) is 10 to 30 parts byweight.

When the ratio of (B) is less than 10 parts by weight, there may not beprovided enough thixotropic properties for screen printing, resulting inpoor printability. On the other hand, when the ratio of (B) exceeds 300parts by weight, printability also tends to lower as fluidity of thepaste is impaired. When the ratio of (C) is less than 1 part by weight,the degree of crosslinking of the dried version of the paste becomesinsufficient, which tends to make the paste composition easilydissoluble in the sealer composing resins at the sealer moldingtemperature, resulting in reduced resistance to package cracking insolder reflowing. Resistance to dissolution in solvent also tends tolower. When the ratio of (C) exceeds 30 parts by weight, the degree ofcrosslinking of the dried version of the paste runs too high, whichtends to impair adhesion (especially heat bonding) to the semiconductorchip or lead frame. Also, in this case, there is a tendency to suppressthe effect of improving resistance to dissolution in solvent.

The thermoresistance adhesive solution and the thermoresistance resinpaste according to the present invention are preferably designed to havea thixotropy factor of 1.5 or above, more preferably 2.0 to 5.0, tobenefit screen printing. When the thixotropy factor is less than 1.5, itis hard to obtain the desired resolution. It is also desirable that thepaste has a viscosity of 10 to 500 Pa·s. When the viscosity is less than10 Pa·s, it is hardly possible to obtain the desired resolution, andwhen the viscosity exceeds 500 Pa·s, transferability and printabilitytend to deteriorate. The viscosity is more preferably 50 to 400 Pa·s,especially 100 to 400 Pa·s. Here, the thixotropy factor is expressed asη₁/η₁₀, or the ratio of apparent viscosity at speed of 1 rpm (η₁) toapparent viscosity at 10 rpm (η₁₀), as measured by an E-type viscometer(EHD-U mfd. by Tokyo Keiki KK) at 25° C. using 0.4 g of sample.Viscosity is represented by apparent viscosity at 0.5 rpm, η_(0.5).

The said thermoresistance adhesive solution and thermoresistance resinpaste can be produced by dissolving or dispersing the componentmaterials in an organic solvent. In case the inorganic or organicparticles are contained, such particles are preferably added anddispersed in an organic solvent solution of a heat-resistant resin. Whenthe organic particles are dispersed, the solid heat-resistant resin usedas material of the organic particles may be added while beingpulverizedid.

The thermoresistance adhesive solution and thermoresistance resin pastecontaining a heat-resistant resin dissolved in an organic solvent andthe organic particles dispersed in an organic solvent can be producedefficiently by the following process.

The thermoresistance resin paste producing process comprises mixing (I)a heat-resistant resin A which is soluble in the solvent of (III) atroom temperature and at the temperature used for heat drying, (II) aheat-resistant resin B which is insoluble in the solvent of (III) atroom temperature but soluble at the temperature used for heat drying,and (III) a solvent, heating the mixture to dissolve the materials, andthen cooling the resulting solution to have the fine particles of theheat-resistant resin B of (II) precipitated and dispersed in thesolution of the heat-resistant resin A of (I) and the solvent of (III).

The heat-resistant resin A serves as the main resin component of saidthermoresistance resin paste, while the heat-resistant resin Bconstitutes the organic particles of said thermoresistance resin paste.Therefore, the heat-resistant resin A is soluble in the solvent at roomtemperature and at the temperature used for heat drying, while theheat-resistant resin B is insoluble in the solvent at room temperaturebut soluble at the temperature used for heat drying, and when a film ofsaid thermoresistance resin paste is formed by screen printing or othermeans., and heat dried to form a film pattern, said both resins A and Bexist as a homogeneous phase after heat drying.

In consideration of solvent stability, solubility of the resin B in thesolvent and productivity, the resin B/solvent combination for use in thepresent invention is preferably one of those shown in Table 1.Especially a combination in which the heat-resistant resin B is anaromatic polyimide resin obtained by reacting an aromatictetracarboxylic acid dianhydride containing 50 mol % or more ofbis(3,4-dicarboxyphenyl)ether dianhydride and an aromatic diaminecontaining 50 mol % or more of 2,2-bis[4-(4-aminophenoxy)phenyl]propane,and the solvent is γ-butyrolactone, is preferably used in view ofsolvent stability, solubility of the resin B in the solvent andproductivity. However, the resin B/solvent combinations usable in thepresent invention are not limited to those mentioned above. The heatdrying temperature for the thermoresistance resin paste comprising anyof the above combinations is usually 50 to 35° C., and it is desirableto effect rise of temperature stepwise from a low temperature to a hightemperature within the above-defined limits.

In the above thermoresistance resin paste producing process, thetemperature used for heat dissolving is not specifically defined as faras the mixture of (I) to (III) can be made into a substantiallyhomogeneous transparent solution, but usually the dissolving operationis preferably conducted with stirring at 80 to 250° C. The time used fordissolution is optional, but it is usually 0.1 to 5 hours, preferably 1to 5 hours. Cooling of the resulting solution can be conducted undersuitable conditions that allow precipitation and dispersion of the fineparticles of heat-resistant resin B in a mixed solution ofheat-resistant resin A and solvent (III), but usually such cooling ispreferably effected by allowing the solution to stand at −20° C. to 100°C. under stirring or in a stationary state for one hour to 60 days. Forforming the fine particles in a short time, cooling is more preferablyconducted with stirring at a specified temperature of from 0° C. to 80°C. for a period of 5 to 80 hours. The rate of cooling from the heatdissolving temperature to the above-defined temperature range of −20° C.to 100° C. may be optionally selected, but it should be noted that rapidcooling tends to induce agglomeration of the precipitated particles, sothat usually cooling is preferably performed with stirring at a rate of0.1 to 10° C./min. The production process is preferably carried out inan inert atmosphere such as an atmosphere of dry nitrogen gas.

According to the thermoresistance resin paste producing process of thepresent invention, the fine particles of heat-resistant resin B aredirectly precipitated from a homogeneous solution of heat-resistantresin A and solvent (III), so that in comparison with the conventionalprocess in which the fine particles are once recovered as solid powderby a suitable method—such as mechanical grinding of the powder recoveredfrom the resin solution, forming of the fine particles under highshearing force while adding the resin solution to a poor solvent, ordrying of the atomized oily droplets of the resin solution to form thefine particles—and the fine particles are dispersed in a heat-resistantresin composition by mechanical milling such as roll milling or ballmilling, the process of the present invention is simple, uncostly andcapable of producing the paste with little ionic contamination.

The preferred mixing ratios of heat-resistant resin A, heat-resistantresin B and solvent (III) in the paste according to the presentinvention are as follows: To 100 parts by weight of heat-resistant resinA, preferably heat-resistant resin B is 10 to 300 parts by weight andsolvent (III) is 50 to 3,000 parts by weight, more preferably resin B is20 to 200 parts by weight and solvent (III) is 75 to 2,000 parts byweight, most preferably resin B is 20 to 200 parts by weight and solvent(III) is 100 to 1,000 parts by weight. When the ratio of heat-resistantresin B is less than 10 parts by weight, the produced paste may fail tohave required thixotropic properties for screen printing, resulting inunsatisfactory printability of the paste. When the resin B ratio exceeds300 parts by weight, fluidity of the paste tends to lower, which alsoleads to unsatisfactory printability. When the ratio of solvent (III) isless than 50 parts by weight, the paste may lack in fluidity anddeteriorate in printability. When its ratio exceeds 3,000 parts byweight, the paste is reduced in viscosity, making it difficult to form athick film and impairing resolving performance.

In the above process, heat-resistant resin A, heat-resistant resin B andsolvent (III) may be mixed in an arbitrary order and heatedsimultaneously with or after mixing to form a homogeneous solvent. Also,resin A and resin B may be severally mixed with solvent (III), followedby further mixing under heating. Heating may be conducted after mixingor simultaneously with mixing to prepare a homogeneous solution.

Further, in the above thermoresistance resin paste producing process,the material of heat-resistant resin B may be supplied into a solutionof heat-resistant resin A and solvent (III), and after dissolving thematerial in the solution, they may be reacted at a temperature whichdoes not cause precipitation of resin B in the solution of resin A andsolvent (III) to synthesize heat-resistant resin B, followed by coolingto have the fine particles of resin B precipitated and dispersed in thesolution of resin A and solvent (III). This is also a preferable methodin the present invention. As the material of heat-resistant resin B,those mentioned above can be used.

In the above thermoresistance resin paste producing process, it is alsoa preferable method to supply the material of heat-resistant resin Ainto a solution of heat-resistant resin B and solvent (III), react themixture (after said material has been dissolved) at a temperature whichdoes not cause precipitation of the fine particles of resin B in thesolution of resin B and solvent (III) to synthesize heat-resistant resinA, and then cool the solution to have the fine particles of resin Bprecipitated and dispersed in the solution of resin A and solvent (III).As the material of heat-resistant resin A, those mentioned above can beused.

According to these methods, it is possible to produce thethermoresistance resin paste consecutively with a single reactionvessel, which contributes to simplification of the process andprevention of contamination with foreign materials such as dust from theworking environment.

In the present invention, the fine particles of heat-resistant resin Bare used for affording thixotropic properties to the paste. As for thesize of the fine particles of heat-resistant resin B, consideringcompatibility of resin B with resin A, thixotropic properties and thinfilm forming properties, it is desirable that the particles beprecipitated and dispersed with the maximal particle size not exceeding10 μm, preferably falling in the range of 0.05 to 5 μm. When the maximalparticle size is less than 0.05 μm, thixotropic properties of the pasteare intensified too much with a small content of the particles.Therefore, the content of the fine particles of heat-resistant resin Bin the paste is reduced, making it difficult to increase the resinconcentration. The particle size can be controlled by, for instance,adjusting the stirring rate and temperature used for precipitating theparticles. The higher the stirring rate or temperature, the smallerbecomes the particle size. It is preferable to select an appropriatetemperature that causes precipitation of the resin B particles frombetween room temperature and 100° C.

In the above thermoresistance resin paste producing process, in case aheat-resistant resin having functional groups such as hydroxyl, amino orcarboxyl group in the molecule is used as resin A, it is possible to adda crosslinking agent having functional groups chemically bondable to theaforesaid functional groups (such as hydroxyl, amino or carboxyl group)after the paste has been formed by dispersing the fine particles ofresin B in the solution of resin A and solvent (III). The additiveswhich are optionally used as required are preferably added after thepaste has been formed by dispersing the fine particles of resin B in thesolution of resin A and solvent (III).

The thermoresistance adhesive according to the present inventionpreferably has a glass transition temperature lower than the adhesiontemperature of a semiconductor chip and the inner leads of a lead frame.Considering adhesion between the semiconductor chip and the inner leadsof lead frame, it is desirable that the glass transition temperature ofsaid adhesive is 20 to 50° C. lower than the adhesion temperature.

The thermoresistance adhesive according to the present invention istypically the one whose temperature of 1% weight loss on heating ispreferably 350° C. or above, more preferably 380° C. or above. When thesaid temperature is below 350° C., outgassing is liable to take place inthe high-temperature heat treatment steps, for example, in the wirebonding operation, making it unable to secure reliability of theproduced semiconductor device. The temperature causing weight loss onheating can be determined by TG-DTA300 (mfd. by Seiko Instruments Inc.Co., Ltd.) at a heating rate of 10° C./min in the air using 10 mg ofsample.

Sealers are essentially composed of base resin, curing agent resin,curing accelerator, modifier, and organic or inorganic filler. Of thesematerials, base resin and curing agent resin are specified in thepresent invention. Examples of such base resin and curing agent resinusable in the present invention include epoxy resins, phenolic resins,bismaleimide resins, epoxysilicone resins, phenolic silicone resins,silicone resins, diallyl phthalate resins, alkyd resins,dicyclopentadiene-phenol addition compounds, dicycloepoxy resinsproduced by reacting epichlorohydrin with dicyclopentadiene-phenoladdition compounds, and phenolamino group-containing compound-formalinaddition compounds. Of these resins, preferred are epoxy resins andphenolic resins which excel in moldability, molded product quality andeconomy and are popularly used in the art.

In the present invention, it is possible to use all types of epoxyresins as far as they contain at least two epoxy groups in the molecule,examples of such epoxy resins including epi-bis type epoxy resins suchas bisphenol A, bisphenol AD, bisphenol S, bisphenol F and halogenatedbisphenol A and epichlorohydrin condensates, biphenyl type epoxy resins,orthocresol novolak epoxy resins, phenolic novolak epoxy resins,bisphenol A novolak epoxy resins, and halides of these epoxy resins,such as brominated phenolic novolak resins and brominated epi-bis typeepoxy resins.

It is also possible to use all types of phenolic resins containing atleast two phenolic hydroxyl groups in the molecules, examples of suchphenolic resins including phenolic novolak resins, cresol novolakresins, bisphenol A novolak resins, poly-p-vinylphenol, phenolic aralkylresins, and xylylene phenolic novolak resins.

As epoxy resin in the present invention, it is preferred to use epi-bisepoxy resins, biphenyl epoxy resins, orthocresol novolak epoxy resins,brominated phenolic novolak epoxy resins and brominated epi-bis epoxyresins as they excel in moldability, molded product quality and economyand are popularly used in the art.

The thermoresistance adhesive according to the present invention ischaracterized by the fact that it does not dissolve in the sealercomposing resins at the sealer molding temperature, and naturally doesnot dissolve in the sealers themselves at their molding temperature.

In the present invention, the sealer molding temperature of 120 to 200°C. is selected as a preferred condition as this range of temperature isgenerally adopted for the treatments of the sealer composing resins. Thethermoresistance adhesive of the present invention does not dissolve inthe sealer composing resins in this range of molding temperature. Thetime in which the thermoresistance adhesive is allowed to contact withthe sealer composing resins at the molding temperature is preferablydefined to 3 to 150 seconds which is the actual molding time of thesealer.

The thermoresistance adhesive according to the present invention iscapable of bonding a semiconductor chip and a lead frame with anadhesive strength under shear of 1 N/4 MM² or greater. Consideringreliability of the produced semiconductor device, such adhesive strengthunder shear is preferably 5 N/4 mm² or greater, more preferably 10 N/4mm² or greater. The greater the adhesive strength under shear, the moredesirable. In the present invention, it is possible to provide anadhesive strength under shear of as high as 60 N/4 mm²or even greater,up to a maximum of about 200 N/4 mm².

The thermoresistance adhesive solution or thermoresistance resin pasteaccording to the present invention may be applied on a semiconductorchip and dried to obtain a semiconductor chip having a thermoresistanceadhesive layer.

Also, the thermoresistance adhesive solution or thermoresistance resinpaste of this invention may be applied to a lead frame and dried toobtain a lead frame having a thermoresistance adhesive layer.

Further, the thermoresistance adhesive solution or thermoresistanceresin paste according to this invention may be applied on one side orboth sides of a support film such as a polyimide film, polyester film orpolycarbonate film and dried to obtain a film having a thermoresistanceadhesive layer.

Various methods such as spin coating, dispensing, potting and printingcan be employed for said application of the thermoresistance adhesivesolution or thermoresistance resin paste of the present invention. It isremarkable that in accordance with the present invention, a thick-filmhigh-precision fine pattern can be produced with good productivity andat low cost by a single coating operation by applying a heat-resistantresin composition having a viscosity of 100 to 400 Pa·s and a thixotropyfactor of 2.0 to 5.0 by printing method and drying the coating. Theprinting method is preferably screen printing.

The temperature for heat drying of the thermoresistance adhesivesolution or thermoresistance resin paste of the present invention ispreferably set at 350° C. or lower, more preferably 300° C. or lower,even more preferably 280° C. or lower. When the drying temperature ishigher than 350° C., the intermolecular reaction of the heat-resistantresin tends to advance excessively, lowering fusibility and adhesiveness(heat bonding properties) of the adhesive or paste. It usually sufficesfor the purpose to conduct drying at 50 to 350° C. for one to 150minutes.

The said polyimide precursor or polyamideimide resin precursor ispreferably subjected to ring-closing reaction in the course of heatdrying to effect imidization.

The thermoresistance adhesive of the present invention is fused at thebonding temperature after said heat drying to effect heat bonding of theadherends. The adhesive is not subject to any specific restrictionsexcept that it should be the one which can be fused in its entiretyafter heat drying to effect desired heat bonding, but it is especiallypreferable that the components of the adhesive, i.e. heat-resistantresins, their reaction products or the reaction products with othercomponents and, in some cases, the organic particles, are all capable ofbeing fused at the bonding temperature.

The thus obtained semiconductor chip or lead frame having athermoresistance adhesive layer is heat bonded to a lead frame orsemiconductor chip, respectively. Heat bonding is usually conducted at200 to 400° C. under a load of 0.1 to 10 MPa for a period of 0.1 to 10seconds. In order to minimize damage to the semiconductor chip (such asdisconnection of the electric circuits), it is desirable that thebonding operation be conducted at a lowest possible temperature under asmallest possible load for a shortest possible period.

Adhesion by use of the adhesive tape, adhesive film or adhesive sheetaccording to the present invention is effected by pressing the adherendto the adhesive side of said tape, film or sheet and bonding thesemiconductor chip and the lead frame simultaneously or in any desiredorder. In the case of an adhesive tape, adhesive film or adhesive sheethaving an adhesive applied on one side alone of the base, thesemiconductor chip or lead frame is bonded to the adhesive-applied sideand the adhesive layer of the lead frame or semiconductor chip isattached to the no-adhesive side of the base. It is also possible tobond the lead frame or semiconductor chip to the no-adhesive side of thebase by interposing therebetween an adhesive tape, film or sheet made ofthe thermoresistance adhesive alone.

Bonding by the thermoresistance adhesive according to the presentinvention is preferably conducted at 200 to 400° C under a load of 0.1to 10 MPa. The bonding time may be properly decided depending on thesituation, but usually a period of 0.1 to 10 seconds is sufficient.

By using a thermoresistance adhesive solution, a film having athermoresistance adhesive layer, a semiconductor chip having athermoresistance adhesive layer and a lead frame having athermoresistance adhesive layer according to the present invention, itis possible to produce a high-capacity and high-reliabilitysemiconductor device by a simple process in a high yield and at lowcost. For example, a semiconductor device can be produced by bonding theplural inner leads of lead frame on the circuit-forming surface of eachsemiconductor chip with the intervention of the thermoresistanceadhesive of the present invention which electrically insulates thesemiconductor chip, then electrically connecting the semiconductor chipand the inner leads of lead frame by means of wire bonding, and finallysealing with a sealer.

It is also possible to produce a semiconductor device by bonding theinner leads of lead frame on the circuit-forming surface of eachsemiconductor chip having a thermoresistance adhesive layer of thisinvention with the intervention of a thermoresistance adhesive layer,electrically connecting the semiconductor chip and the inner leads oflead frame by wire bonding, and sealing with a sealer.

A semiconductor device can also be produced by bonding the inner leadsof lead frame having a thermoresistance adhesive layer of this inventionon the circuit-forming surface of each semiconductor chip with theintervention of a thermoresistance adhesive layer, electricallyconnecting the semiconductor chip and the inner leads of lead frame bywire bonding, and sealing with a sealer.

In the semiconductor device according to the present invention, it isdesirable that the entirety of the circuit-formed area, excepting thebonding pad of each semiconductor chip and fuse circuit, be covered witha film of a heat-resistant resin such as polyimide resin. Thisheat-resistant resin film serves as a circuit protective film or anα-ray shield. It also contributes to lessening chip damage (such asdisconnection of electric circuits) when applying a heat-resistant resincomposition containing the inorganic or organic particles of thisinvention on the semiconductor chip by screen printing.

The semiconductor chip used in the present invention is preferably theone having a thermoresistance adhesive layer obtained by attaching aperforated adhesive-applied metal or resin film with a Young's modulusof 2 GPa or greater to a semiconductor wafer, injecting saidheat-resistant resin or heat-resistant resin composition into the holesin the film by a dispenser or other means, squeegeing the film, thenpeeling the film after drying if necessary, and dicing it. According tothis method, a thermoresistance adhesive layer can be formed withminimized risk of chip damage (such as disconnection of electriccircuits).

As bonding wire in the present invention, there can be used Au wire, Alwire, Cu wire or the like.

As lead frame, for instance the one made of a Fe—Ni alloy (Ni content:42% or 50%) or Cu may be used.

The semiconductor device according to the present invention may have thestructures such as illustrated in FIGS. 1 to 3.

FIG. 1 is a schematic sectional view of a semiconductor device producedby bonding each semiconductor chip 2 and lead frame 3 through the mediumof a thermoresistance adhesive 1 applied only at the portion to bebonded of the lead frame, and sealing the semiconductor chip 2, thebonded portion of semiconductor chip 2 and lead frame 3, and the bondingwires 5 by a sealer, wherein the semiconductor chip 2 is positionedbeneath the lead frame 3.

FIG. 2 is a schematic sectional illustration of a semiconductor deviceproduced by bonding each semiconductor chip 2 and lead frame 3 throughthe medium of a heat-resistant resin layer 1 formed over the entirecircuit-formed area excepting the bonding pad of semiconductor chip 2and the fuse circuit, and sealing the semiconductor chip 2, the bondedportion of semiconductor chip 2 and lead frame 3 and the bonding wires 5by a sealer, wherein the semiconductor chip 2 is positioned beneath thelead frame 3.

FIG. 3 is a schematic sectional view of a semiconductor device producedby forming a thermoresistance adhesive layer 1 over the entirecircuit-formed area excepting the bonding pad of semiconductor chip 2and the fuse circuit as a buffer coat, bonding the semiconductor chip 2and lead frame 3 through the medium of the thermoresistance adhesivelayer 1 formed over the whole rear side of the semiconductor chip 2, andsealing the semiconductor chip 2, the bonded portion of semiconductorchip 2 and lead frame 3 and the bonding wires 5 by a sealer, wherein thesemiconductor chip 2 is positioned upwards of the lead frame 3.

In a preferred mode of practice of such semiconductor device producingprocess, a thermoresistance adhesive layer is formed on thesemiconductor chip by applying a heat-resistant resin or aheat-resistant resin composition over the entire surface of the chipexcepting the wire bonding pad or at the portion to be bonded to thelead frame, the lead frame is heat bonded under pressure to saidthermoresistance adhesive layer of the conductor chip, then the leadframe and semiconductor chip are joined by Au wire or such, and theelements are sealed by transfer molding with an epoxy resin sealer.

The present invention will be further illustrated by the followingExamples and Comparative Examples, but the present invention is notlimited thereto.

EXAMPLE 1

To a 1,000 ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 36.00 g (0.18 mol) of 4,4′-diaminodiphenyl ether (hereinafterabbreviated to DDE), 73.90 g (0.18 mol) of2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter abbreviated toBAPP), 9,93 g (0.04 mol) of 1,3-bis(aminopropyl)tetramethyldisiloxane,128.8 g (0.40 mol) of 3,4,3′,4′-benzophenonetetracarboxylic aciddianhydride (hereinafter abbreviated to BTDA) and 373 g ofγ-butyrolactone (hereinafter abbreviated to BL) were supplied whileblowing nitrogen gas through the solution. Reaction was allowed toproceed with stirring at 50 to 60° C. for 5 hours to obtain a polyamideacid resin solution with a resin content of 40 wt %.

This polyamide acid resin solution was bar coated on a glass plate(approximately 2 mm thick) to a coating thickness after heat drying of20 μm, and heat treated at 140° C. for 15 minutes, at 200° C. for 15minutes and then at 300° C. for 60 minutes to imidizate the polyamideacid to obtain a glass plate having a polyimide resin coating film. Thispolyimide resin coated glass plate was heated to 180° C., and about 0.1g of pellets of each of the sealer-composing resins, viz. YX-4000H(trade name of a bisphenyl epoxy resin produced by Yuka Shell Co.,Ltd.), ESCN-190 (trade name of an orthocresol novolak epoxy resinproduced by Sumitomo Chemical Co., Ltd.), HP-850N (trade name of aphenolic novolak resin produced by Hitachi Chemical Company, Ltd.) andXL-225 (trade name of a xylylene phenolic novolak resin produced byMitsui Chemicals, Inc.) were placed severally on the polyimide resincoating film of said glass plate and allowed to stand at 180° C. for 2minutes, after which the molten resin left on the polyimide resincoating film was wiped off at the same temperature. A film dissolvingtest was conducted by observing the condition of dissolution of thepolyimide resin coating film in said sealer-composing resins. As aresult, in the case of the orthocresol novolak epoxy resin ESCN-190,there was observed no change at all in appearance of the film,indicating that the polyimide resin film does not dissolve in saidsealer resin. In the case of the biphenyl epoxy resin YX-4000H and thephenolic novolak resin HP-850N, although a sign of dissolution wasadmitted at the area contacted with the resin pellets, there was notedno formation of hollows or holes in the polyimide resin coating filmthat could have resulted from dissolution of the film in these resinsand consequent formation of a molten fluid, indicating that thepolyimide resin coating film does not dissolve in these sealer resins.

The polyimide resin coating film was peeled off said coated glass plate,and the glass transition temperature (Tg) of the separated film (cutinto a 3 mm×20 mm test piece) was determined by a thermophysical testerTMA-120 (mfd. by Seiko Instruments Inc.) under a load of 8 g at aheating rate of 5° C. It was found that Tg was 235° C.

The above polyamide acid resin solution was bar coated on a siliconwafer (approximately 0.65 mm thick) to a coating thickness after heatdrying of 20 μm, and heat treated at 140° C. for 15 minutes, at 200° C.for 15 minutes and at 300° C. for 60 minutes to imidizate the polyamideacid to obtain a silicon wafer having a polyimide resin coating film.This polyimide resin coated silicon wafer was diced to obtain a 2 mm×2mm polyimide resin coated silicon chip. This polyimide resin coatedsilicon chip was heat bonded to a Fe—Ni alloy (Ni content: 42%,hereinafter referred to as 42 alloy) plate for lead frame, with thepolyimide resin coating film serving as an adhesive layer, under theconditions of 300° C., 0.2 MPa and 5 seconds, and its adhesive strengthunder shear was measured by Dage's automatic adhesion tester MicrotesterBT-22 (measuring temperature: 25° C.; testing rate: 0.5 mm/S). Theadhesive strength under shear thus determined was 2.5 N/2×2 mm².

The above polyamide resin solution was diluted with BL to a viscosity of10 Pa·s, applied on a semiconductor substrate (wafer) by a coater(SC-W80A mfd. by Dainippon Screen Mfg. Co., Ltd.), and heat treated(pre-baked) on a hot plate at 90° C. for 120 seconds to obtain a 19 μmthick pre-baked film. On this pre-baked film was applied a phenolicnovolak photo-sensitive resin (positive photoresist for soldering, tradename: OFPR-5000, produced by Tokyo Ohka Kogyo Co., Ltd.) by using thesaid coater to form a positive resist layer. Then, in order toselectively remove the bonding pad portion and the scribing line alone,the 100 μm square bonding pad and 70 μm scribing line width were exposedby photoetching to melt the irradiated area, and then the development ofthe positive resist layer and etching of the pre-baked film wereconducted continuously at 23° C. for 160 seconds by using an aqueoustetramethylammonium hydroxide solution developer (trade name: NMD-3produced by Tokyo Ohka Kogyo Co., Ltd.) as etching solution to exposethe bonding pad portion. Then a resist releasing solution (n-butylacetate) for etching the positive resist layer alone was applieddropwise over the whole wafer surface from a spray nozzle and treated atroom temperature for 90 seconds to perfectly remove the positive resistlayer. Then the wafer was put into a hot air dryer and heat treated at200° C. for 15 minutes, at 250° C. for 15 minutes and at 300° C. for 60minutes to imidizate the polyamide acid to obtain a wafer having a 15 μmthick polyimide resin coating film, and this polyimide resin coatedwafer (0.65 mm thick) was diced to obtain a polyimide resin coatedsemiconductor chip. To the polyimide resin coating film of thissemiconductor chip was heat bonded a 42 alloy-made lead frame 3, asshown in FIG. 2, under the conditions of 300° C., 0.1 MPa and 5 seconds.Then, the lead frame and the semiconductor chip were joined by Au-madebonding wires 5 and sealed by transfer molding with a biphenyl epoxyresin sealer CEL-9200 (trade name, produced by Hitachi Chemical Company,Ltd.) containing said four sealer-composing resins. The adhesiveinterface between the polyimide resin coating film and the sealer layerof the semiconductor device (package) having the structure shown in FIG.2 was examined by a supersonic flaw detector, but no exfoliation at theinterface was observed (0/30, which means none of 30 samples sufferedexfoliation). The obtained semiconductor device (package) was allowed toabsorb moisture by leaving it in an atmosphere of 85° C. and 85% RH for168 hours and subjected to infrared reflowing (240° C., 10 seconds), butno package crack was observed (0/30, which means none of 30 samples hadcracks).

EXAMPLE 2

To a 1,000 ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 65.69 g (0.16 mol) of BAPP, 143.22 g (0.40 mol) ofbis(3,4-dicarboxylphenyl)sulfone dianhydride (hereinafter abbreviated toDSDA), 38.84 g (0.20 mol) of isophthalic acid dihydrazide (hereinafterabbreviated to IPDH), 9.93 g (0.04 mol) of1,3-bis(aminopropyl)tetramethyldisiloxane and 478 g of BL were suppliedwhile blowing nitrogen gas through the solution. After one-hour reactionat 50 to 60° C. with stirring, the temperature was raised to 195° C. andthe reaction was continued at this temperature for 6 hours. Watergenerated in the course of the reaction was rapidly removed out of thereaction system. The resulting solution was diluted with BL to obtain apolyamide-imide resin solution with a resin concentration of 30% byweight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 102.64 g (0.25 mol) of BAPP, 77.55 g (0.25 mol) ofbis(3,4-dicarboxyphenyl)ether dianhydride (hereinafter abbreviated toODPA) and 335 g of BL were supplied while blowing nitrogen gas throughthe solution. After conducting the reaction at 50 to 60° C. for one hourwith stirring, the temperature was raised to 195° C. and the reactionwas allowed to proceed at this temperature for 5 hours. Water generatedduring the reaction was rapidly removed out of the reaction system. Theresulting solution was diluted with BL to a resin concentration of 30%by weight and allowed to stand at 23° C. for one month to give a solidpolyimide resin for filler containing the solvent.

To a 1,000 ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 200 g of saidsolvent-containing solid polyimide resin for filler (resinconcentration: 30 wt %) in the pulverized form was supplied and heatedto 180° C. The solution was stirred at this temperature for one hour toform a homogeneous solution, and to this solution was added 466.67 g ofthe previously prepared polyamide-imide resin solution (resinconcentration: 30 wt %), followed by one-hour stirring at 180 C. Themixed a solution was cooled to 23° C. over a period of about one hourand allowed to stand as such for one month. As a result, the finepolyimide resin particles were precipitated and dispersed in thesolution to give a polyimide resin paste having a viscosity of 380 Pa·sand a thixotropy factor (hereinafter referred to as TI value) of 2.9.The recovered polyimide resin particles had a maximal size of 20 μm andwas insoluble in BL at room temperature but soluble at 150° C.

Using the above polyimide resin paste, a glass plate having a polyimideresin coating film was obtained in the same way as in Example 1. Thiscoating film was homogeneous and transparent, indicating that thepolyimide resin particles in the polyimide resin paste were dissolved inBL in the process of curing and were also sufficiently compatible withthe polyamide-imide resin. The state of dissolution of this polyimideresin coating film in the sealer-composing resins was examined in thesame way as in Example 1. As a result, in the case of the orthocresolnovolak epoxy resin ESCN-190, there was seen no change at all inappearance of the film, indicating that the coating film does notdissolve in this resin. In the case of the biphenyl epoxy resinYX-4000H, phenol novolak resin HP-850N and xylylene phenolic novolakresin XL-225, although a trace of dissolution was admitted at the areacontacted with the resin pellets, there was observed no formation ofhollows or holes in the polyimide resin film attributable to itsdissolution in these resins and consequent formation of a molten fluid,indicating that the coating film does not dissolve in these resins. Tgof the coating film, as measured in the same way as in Example 1, was256° C. Using the said polyimide resin paste, the adhesive strengthunder shear to a 42 alloy plate was determined in the same way as inExample 1 except that bar coating on a silicon wafer (approximately 0.65mm thick) was replaced by screen printing. The adhesive strength was 5.0N/2×2 mm².

The said polyimide resin paste was coated over the whole chip surfaceexcepting the bonding pad portion by using a screen printer (LS-34GXwith aligning means, mfd. by Newlong Seimitsu Kogyo Co., Ltd.), and heattreated at 140° C. for 15 minutes, at 200° C. for 15 minutes and at 300°C. for 60 minutes to obtain a semiconductor wafer with a 18 μm thickpolyimide resin coating film. The adhesive interface between thepolyimide resin coating film and the sealer layer of a semiconductordevice (package) obtained in the same way as in Example 1 using saidsemiconductor wafer was examined by a supersonic flaw detector. Therewas observed no exfoliation at the interface (0/30). Also, thesemiconductor device (package) was allowed to absorb moisture by leavingit in an atmosphere of 85° C. and 85% RH for 168 hours and thensubjected to infrared reflowing (240° C., 10 seconds). No package cracktook place (0/30).

EXAMPLE 3

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser with an oil/water separator,102.64 g (0.25 mol) of BAPP, 127.83 g (0.357 mol) of DSDA, 23.13 g(0.107 mol) of 2,2-bis(4-hydroxy-3-aminophenyl)propane (hereinafterabbreviated to HAB) and 380 g of N-methylpyrrolidone (hereinafterabbreviated to NMP) were supplied while blowing nitrogen gas through thesolution. After one-hour reaction at 50 to 60° C. with stirring, thetemperature was raised to 195° C. and the reaction was continued at thistemperature for 5 hours. Water generated in the course of the reactionwas rapidly removed out of the reaction system. The resulting solutionwas diluted with NMP to obtain a polyimide resin solution with a resinconcentration of 40% by weight.

To 200 g of this polyimide resin solution was added 8 g ofγ-glycidoxypropyltrimethoxysilane (hereinafter abbreviated to GPS),followed by mixing well at room temperature to obtain a polyimide resincomposition.

Using this polyimide resin composition, a glass plate with a polyimideresin composition coating film was obtained in the same way as inExample 1. Dissolubility of this polyimide resin composition coatingfilm in the sealer-composing resins was examined in the same way as inExample 1. As a result, in the case of the orthocresol novolak epoxyresin ESCN-190, there was observed no change at all in appearance of thefilm, indicating that the coating film does not dissolve in this resin.In the case of the biphenyl epoxy resin YX-4000H, phenolic novolak resinHP-850N and xylylene phenolic novolak resin XL-225, although a trace ofdissolution was admitted in the area contacted with the resin pellets,there was observed no formation of hollows or holes in the coating filmattributable to its dissolution in these resins and consequent formationof a molten fluid, indicating that the coating film does not dissolve inthese resins. Tg of the coating film, as determined in the same way asin Example 1, was 262° C. The adhesive strength under shear of saidpolyimide resin composition to a 42 alloy plate, as determined in thesame way as in Example 1, was 11 N/2×2 mm².

The above polyimide resin composition was coated on both sides of a 50μm thick polyimide film (Upilex S produced by Ube Industries, Ltd.) sothat the coating thickness on each side of the film after heat dryingwould become 25 μm, and then heat treated at 140° C. for 15 minutes, at200° C. for 15 minutes and at 300° C. for 60 minutes to obtain apolyimide resin composition coated film. This coated film was cut to asize of 1.5 mm×10 mm and placed between a 42 alloy-made lead frame 3 anda semiconductor chip 2 as shown in FIG. 1, and they were heat bondedunder the conditions of 300° C., 0.2 MPa and 5 seconds. Then, the leadframe and the semiconductor chip were joined by Au bonding wires 5 andsealed by transfer molding with a biphenyl epoxy resin sealer CEL-9200(trade name, produced by Hitachi Chemical Company, Ltd.). The adhesiveinterface between the polyimide resin composition coating film and thesealer layer of the obtained semiconductor device (package) was examinedby a supersonic flaw detector. There was observed no exfoliation at theinterface (0/30). The semiconductor device (package) was allowed toabsorb moisture by leaving it in an atmosphere of 85° C. and 85% RH for168 hours and then subjected to infrared reflowing (240° C., 10seconds). There took place no package cracking (0/30).

EXAMPLE 4

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 89.09 g (0.217 mol) of BAPP, 119.59 g (0.334 mol) of DSDA,42.85 g (0,117 mol) of 2,2-bis(4-hydroxy-3-aminophenyl)hexafluoropropane(hereinafter abbreviated to HAB-6F) and 377 g of BL were supplied whileblowing nitrogen gas through the solution. After one-hour reaction at 50to 60° C. with stirring, the temperature was raised to 195° C. and thereaction was continued at this temperature for 5 hours. Water generatedin the course of the reaction was rapidly removed out of the reactionsystem. The resulting solution was diluted with BL to obtain a polyimideresin solution with a resin concentration of 40% by weight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 400 g of thesolvent-containing solid polyimide resin for filler obtained in Example2 (resin concentration: 30 wt %) was supplied in the pulverized form andheated to 180° C. The solution was stirred at this temperature for onehour to form a homogeneous solution, and to this solution was added 300g of said polyimide resin solution (resin concentration: 40 wt %),followed by stirring at 180° C. for one hour. The solution was cooled to23° C. over a period of about one hour and allowed to stand as such forone month. As a result, the fine particles of the polyimide resin wereprecipitated and dispersed in the solution to give a paste. To thispaste, 48 g of GPS was added and mixed well at room temperature, and themixture was diluted with BL to a resin concentration of 36% by weight.The obtained polyimide resin paste had a viscosity of 280 Pa·s and a TIvalue of 3.3. The maximal size of the recovered polyimide resinparticles was 20 μm, and the particles were insoluble in BL at roomtemperature but soluble at 150° C.

Using the above polyimide resin paste, a glass plate having a polyimiderresin coating film was obtained in the same way as in Example 1. Thiscoating film was homogeneous and transparent, indicating that thepolyimide resin particles in said polyimide resin paste were dissolvedin BL in the process of drying and also well compatible with thepolyimide resin. Dissolubility of this polyimide resin coating film inthe sealer-composing resins was examined in the same way as inExample 1. As a result, in the case of the orthocresol novolak epoxyresin ESCN-190, there took place no change at all in appearance of thefilm, indicating that the coating film does not dissolve in this resin.In the case of the biphenyl epoxy resin YX-4000H, phenolic novolak resinHP-850N and xylylene phenolic novolak resin XL-225, although a trace ofdissolution was admitted in the area contacted with the resin pellets,there was observed no formation of hollows or holes in the polyimideresin coating film attributable to its dissolution in these resins andconsequent formation of a molten fluid, indicating that the coating filmdoes not dissolve in these resins. Tg of the coating film, as determinedin the same way as in Example 1, was 256° C. Adhesive strength undershear of said polyimide resin paste to a 42 alloy plate, as determinedin the same way as in Example 1 except that bar coating on a siliconwafer (approximately 0.65 mm thick) was replaced by screen printing, was12 N/2×2 mm².

Using said polyimide resin paste, a semiconductor device (package) wasmade in the same way as in Example 2 except that print coating on thechip surface other than the bonding pad portion was conducted byapplying said polyimide resin paste on the portion of the chip surfacewhere the lead frame was to be bonded, other than the bonding padportion, and exfoliation at the interface between the polyimide resincoating film and the sealer layer was examined by a supersonic flawdetection. There was observed no exfoliation (0/30). Also, thesemiconductor device (package) was allowed to absorb moisture by leavingit in an atmosphere of 85° C. and 85% RH for 168 hours and thensubjected to infrared reflowing (240° C., 10 seconds), during which nopackage cracking occurred (0/30).

EXAMPLE 5

The polyimide resin paste of Example 4 was print coated on the portionof a 42 alloy-made lead frame to be bonded to a semiconductor chip by ascreen printer (LS-34GX with an aligning means, mfd. by Newlong SeimitsuKogyo Co., Ltd.), and then heat treated at 140° C. for 15 minutes, at200° C. for 15 minutes and at 300° C. for 60 minutes to obtain a leadframe having a 18 μm thick polyimide resin coating film. This lead framewas heat bonded to a semiconductor chip 2 as shown in FIG. 1 under theconditions of 300° C., 0.2 MPa and 5 seconds. Then, the lead frame andthe semiconductor chip were joined by Au bonding wires 5 and sealed bytransfer molding with a orthocresol novolak resin sealer CEL7700SX(trade name, produced by Hitachi Chemical Company, Ltd.) 4. The adhesiveinterface between the polyimide resin coating film and the sealer layerof the obtained semiconductor device (package) was examined by asupersonic flaw detector, but no exfoliation was observed (0/30). Also,the obtained semiconductor device (package) was allowed to absorbmoisture by leaving it in an atmosphere of 85° C. and 85% RH for 168hours and then subjected to infrared reflowing (240° C., 10 seconds).There took place no package cracking (0/30).

COMPARATIVE EXAMPLE 1

The same procedure as conducted in Example 1 was carried out except thatthe mixture of DDE and BAPP was replaced by 72.36 g (0.36 mol) of DDEalone, that the acid dianhydride BTDA was replaced by a mixture of 64.48g (0.20 mol) of BTDA and 43.64 g (0.20 mol) of pyromellitic aciddianhydride, and that the solvent BL was replaced by 449 g of NMP toobtain a polyamide acid resin solution.

Using this polyamide acid resin solution, a glass plate having apolyimide resin coating film was obtained in the same way as inExample 1. Dissolubility of this polyimide resin coating film in thesealer-composing resins was examined in the same way as in Example 1. Asa result, with any of the biphenyl epoxy resin YX-4000H, orthocresolnovolak epoxy resin ESCN-190, phenolic novolak resin HP-850N andxylylene phenolic novolak resin XL-225, there was observed no change atall in appearance of the film, indicating that the coating film does notdissolve in these resins. Tg of the coating film, as determined in thesame way as in Example 1, was 305° C. However, when it was tried todetermine the adhesive strength under shear of the coating film to a 42alloy plate by using said polyamide acid resin solution in the same wayas in Example 1, the 42 alloy plate didn't bond at all to the polyimideresin coating film and it was impossible to determine the adhesivestrength.

Using the polyamide acid resin solution diluted with BL to a viscosityof 10 Pa·s, a semiconductor chip having a 16 μm thick polyimide resincoating film with a bonding pad portion was obtained in the same way asin Example 1. It was tried to make a semiconductor device (package) byusing said semiconductor chip in the same way as in Example 1, but the42 alloy-made lead frame didn't bond at all to the polyimide resincoating film of the semiconductor chip and it was impossible to produceand evaluate a semiconductor device.

COMPARATIVE EXAMPLE 2

A polyimide resin solution was obtained by following the same synthesisprocedure as in Example 2 except that instead of using a mixture of BAPPand IPDH of the diamine moiety, 247.8 g (0.36) of BAPP alone was used.Then the process of Example 2 was followed except for use of saidpolyimide resin solution and a solvent-containing solid polyimide resinfor filler of Example 2 to obtain a polyimide resin paste having aviscosity of 230 Pa·s and a TI value of 2.8. The recovered polyimideresin particles had a maximal size of 20 μm or less, and were insolublein BL at room temperature but soluble at 150° C.

Using this polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was homogeneous and transparent. Dissolubility of this polyimideresin coating film in the sealer-composing resins was examined in thesame way as in Example 1. As a result, the coating film dissolved in anyof the bisphenyl epoxy resin YX-4000H, orthocresol novolak epoxy resinESCN-190, phenolic novolak resin HP-850N and xylylene phenolic novolakresin XL-225 to form a molten fluid, and the holes of about 5 mm indiameter reaching the substrate glass plate were formed in the polyimideresin coating film. Tg of the coating film, as measured in the same wayas in Example 1, was 220° C. Adhesive strength under shear of thecoating film to an 42 alloy plate, measured by using said polyimideresin paste in the same way as in Example, was 16 N/2×2 mm².

Said polyimide resin paste was coated on the chip surface excepting thebonding pad portion in the same way as in Example 2 to obtain asemiconductor wafer having a polyimide resin coating film. The adhesiveinterface between the polyimide resin coating film and the sealer layerof a semiconductor device (package) made by using said semiconductorwafer in the same way as in Example 3 was examined. Exfoliation at theinterface was seen in all of the samples tested (30/30, which indicatesthat 30 out of 30 samples suffered exfoliation). When the semiconductordevice (package) was allowed to absorb moisture by leaving it in anatmosphere of 85° C. and 85% RH for 168 hours and then subjected toinfrared reflowing (240° C., 10 seconds), there took place packagecracking in all of the samples tested (30/30).

COMPARATIVE EXAMPLE 3

A polyimide resin solution was obtained by following the same synthesisas in Example 4 except that instead of using a mixture of BAPP andHAB-6F of the diamine moiety, 37.12 g (0.334 mol) of BAPP alone wasused. Then the same procedure as defined in Example 4 was repeatedexcept for use of said polyimide resin solution and thesolvent-containing solid polyimide resin for filler used in Example 2 toobtain a polyimide resin paste having a viscosity of 330 Pa·s and a TIvalue of 3.2. The maximal size of the recovered polyimide resinparticles was 20 μm or less, and the particles were insoluble in BL atroom temperature but soluble at 150° C.

Using this polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was homogeneous and transparent. Dissolubility of this polyimideresin coating film in the sealer-composing resins was examined in thesame way as in Example 1. As a result, the coating film dissolved in anyof the biphenyl epoxy resin YX-4000H, orthocresol novolak epoxy resinESCN-190, phenolic novolak resin HP-850N and xylylene phenolic novolakresin XL-225 to form a molten fluid, and the holes of 5 mm in diameterreaching the base glass plate were formed in the polyimide coating film.Tg of the coating film, measured in the same way as in Example 1, was235° C. Adhesive strength under shear of the coating film to a 42 alloyplate, measured by using said polyimide resin paste in the same way asin Example 1, was 15 N/2×2 mm².

A semiconductor device (package) was made in the same way as in Example2 except that said polyimide resin paste was print coated on the area ofthe chip surface where the lead frame was to be bonded, other than thebonding pad portion, and the adhesive interface between the polyimideresin coating film and the sealer layer of said semiconductor device(package) was examined by a supersonic flaw detector. Exfoliation at theinterface took place in all of the samples (30/30). When thesemiconductor device (package) was allowed to absorb moisture by leavingit in an atmosphere of 85° C. and 85% RH for 168 hours and thensubjected to infrared reflowing (240° C., 10 seconds), package crackingoccurred in all of the samples (30/30).

COMPARATIVE EXAMPLE 4

The same polyimide resin paste preparation process as used in Example 4was conducted except that no GPS was added to obtain a polyimide resinpaste having a viscosity of 360 Pa·s and a TI value of 3.5.

Using this polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was homogeneous and transparent. Dissolubility of this polyimideresin coating film in the sealer-composing resins was examined in thesame way as in Example 1. As a result, the coating film dissolved in anyof the biphenyl epoxy resin YX-4000H, orthocresol novolak epoxy resinESCN-190, phenolic novolak resin HP-850N and xylylene phenolic novolakresin XL-225 to form a molten fluid, and the holes of about 5 mm indiameter reaching the base glass plate were formed in the polyimideresin coating film. Tg of the coating film measured in the same way asin Example 1 was 235° C. Adhesive strength under shear of the coatingfilm to a 42 alloy plate measured by using said polyimide resin paste inthe same way as in Example 1 was 15 N/2×2 mm².

Using said polyimide resin paste, a semiconductor device (package) wasobtained in the same way as in Example 2 except that the paste wasapplied on the area of the chip surface where the lead frame was to bebonded, other than the bonding pad portion, and the adhesive interfacebetween the polyimide resin film and the sealer layer was examined by asupersonic flaw detector. As a result, exfoliation at the interfaceoccurred in 18 of the 30 samples (18/30). Also, when the obtainedsemiconductor device (package) was allowed to absorb moisture by leavingit in an atmosphere of 85° C. and 85% RH for 168 hours and thensubjected to infrared reflowing (240° C., 10 seconds), package crackingtook place in 11 out of the 30 samples (11/30).

COMPARATIVE EXAMPLE 5

A polyimide resin paste having a viscosity of 380 Pa·s and a TI value of3.6 was obtained in the same way as in Example 1 except that anorthocresol novolak epoxy resin ESCN-190 was added, instead of GPS, tothe polyimide resin paste.

Using this polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was homogeneous and transparent. Dissolubility of this polyimideresin coating film in the sealer composing resins was examined in thesame way as in Example 1. As a result, in the case of the biphenol epoxyresin YX-4000H and orthocresol novolak epoxy resin ESCN-190, there tookplace no change at all in appearance of the film, indicating that thecoating film does not dissolve in these resins. In the case of thephenolic novolak resin HP-850N and xylylene pehnolic novolak resinXL-225, although a trace of dissolution was admitted in the areacontacted with the resin pellets, there was observed no formation ofhollows or holes in the coating film attributable to its melting inthese resins and consequent formation of a molten fluid, indicating thatthe coating film does not dissolve in these resins. Tg of the coatingfilm measured in the same way as in Example 1 was 275° C. It was triedto measure adhesive strength under shear of the coating film to a 42alloy plate in the same way as in Example 1 by using said polyimideresin paste, but the 42 alloy plate did not bond at all to the polyimideresin coating film and it was impossible to measure adhesive strength.

Using said polyimide resin paste, a semiconductor wafer having a 18 μmthick polyimide resin coating film was obtained in the same way as inExample 2 by coating the polyimide resin paste on the chip surfaceexcepting the bonding pad portion. This semiconductor wafer was dicedinto a semiconductor chip, and it was tried to make a semiconductordevice (package) by using this semiconductor chip in the same way as inExample 1, but since the 42 alloy-made lead frame did not bond at all tothe polyimide resin coating film of the semiconductor chip, it wasimpossible to make and evaluate a semiconductor device.

COMPARATIVE EXAMPLE 6

A polyimide resin paste having a viscosity of 290 Pa·s and a TI value of3.4 was obtained in the same way as in Example 4 except that4,4′-diphenylmethanebismaleimie (produced by Mitsui Chemicals Inc.) wasadded in place of GPS to the polyimide resin paste.

Using this polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was homogeneous and transparent. Dissolubility of this polyimideresin coating film in the sealer composing resins was examined in thesame way as in Example 1. As a result, in the case of the biphenyl epoxyresin YX-4000H and orthocresol novolak epoxy resin ESCH-190, there tookplace no change at all in appearance of the coating film, indicatingthat the coating film does not dissolve in these resins. In the case ofthe phenolic novolak resin HP-850N and xylylene phenolic novolak resinXL-225, although a trace of dissolution was admitted in the areacontacted with the resin pellets, there was observed no formation ofhollows or holes in the coating film attributable to its dissolution inthese resins and consequent formation of a molten fluid, indicating thatthe polyimide coating film does not dissolve in these resins. Tg of thecoating film measured in the same way as in Example 1 was 280° C. It wastried to determine adhesive strength under shear of the coating film toa 42 alloy plate by using said polyimide resin paste in the same way asin Example 1, but the 42 alloy plate did not bond at all to thepolyimide resin coating film and it was impossible to measure adhesivestrength.

Using said polyimide resin paste, a semiconductor wafer having a 18 μmthick polyimide resin coating film was obtained in the same way as inExample 2 by coating the polyimide resin paste on the chip surfaceexcepting the bonding pad portion. This wafer was diced into asemiconductor chip, and it was tried to make a semiconductor device(package) by using this semiconductor chip in the same way as in Example1, but the 42 alloy-made lead frame did not bond at all to the polyimideresin coating film of the semiconductor chip and it was impossible tomake and evaluate a semiconductor device.

The foregoing results are shown collectively in Table 2 below.

TABLE 2 Properties Example 1 Example 2 Dissolubility in sealer-composingresins YX-4000H Did not dissolve (showed Did not dissolve (showed atrace of dissolution) a trace of dissolution ESCN-190 Did not dissolveDid not dissolve HP-850N Did not dissolve (showed Did not dissolve(showed a trace of dissolution) a trace of dissolution) XL-225 Did notdissolve (showed Did not dissolve (showed a trace of dissolution) atrace of dissolution) Adhesive strength under shear to 2.5 5.0 42 alloyplate (N/mm²) Tg (° C.) 235 256 Early exfoliation of package 0/30 0/30(Number of exfoliated samples/ number of samples tested) Packagecracking (Number of 0/30 0/30 samples which cracked/number of samplestested) Example 3 Example 4 Example 5 Did not dissolve (showed Did notdissolve (showed Did not dissolve (showed a trace of dissolution) atrace of dissolution) a trace of dissolution) Did not dissolve Did notdissolve Did not dissolve Did not dissolve (showed Did not dissolve(showed Did not dissolve (showed a trace of dissolution) a trace ofdissolution) a trace of dissolution) Did not dissolve (showed Did notdissolve (showed Did not dissolve (showed a trace of dissolution) atrace of dissolution a trace of dissolution 11 12 12 262 256 256 0/300/30 0/30 0/30 0/30 0/30 Properties Comp. Example 1 Comp. Example 2Dissolubility in sealer-composing resins YX-4000H Did not dissolveDissolved ESCN-190 Did not dissolve Dissolved HP-850N Did not dissolveDissolved XL-225 Did not dissolve Dissolved Adhesive strength undershear to Did not bond 16 42 alloy plate (N/mm²) (Unmeasurable) Tg (° C.)305 220 Early exfoliation of package — 30/30 (Number of exfoliatedsamples/ (Unmeasurable) number of samples tested) Package cracking(Number of — 30/30 samples which cracked/number of (Unmeasurable)samples tested) Comp. Example 3 Comp. Example 4 Comp. Example 5 Comp.Example 6 Dissolved Dissolved Did not dissolve Did not dissolveDissolved Dissolved Did not dissolve Did not dissolve DissolvedDissolved Did not dissolve (showed Did not dissolve (showed a trace ofdissolution) a trace of dissolution) Dissolved Dissolved Did notdissolve (showed Did not dissolve (showed a trace of dissolution) atrace of dissolution) 15 15 Did not bond Did not bond (Unmeasurable)(Unmeasurable) 235 235 275 280 30/30 18/30 — — (Unmeasurable)(Unmeasurable) 30/30 11/30 — — (Unmeasurable) (Unmeasurable)

As is seen from the results of Comparative Examples 2 to 4, in the caseof the coating film which is dissolved in the sealer composing resins atthe sealer molding temperature (180° C.) to form a molten fluid, a weakadhesive layer is formed at the interface between the sealer and thethermoresistance adhesive, so that there takes place initial exfoliationof the package and also package cracking tends to occur in infraredreflowing after moisture absorption. Also, as is noted from the resultsof Comparative Examples 1, 5 and 6, even if the coating film does notdissolve in the sealer composing resins at the sealer moldingtemperature (180° C.), if Tg of the coating film is too high or theselection of the curing system is improper, there is provided nosufficient adhesive strength under shear to the 42 alloy plate, makingit unable to bond the lead frame and the semiconductor chip. On theother hand, as is learned from the results of Examples 1 to 5, in thecase of a coating film which does not dissolve in the sealer composingresins at the sealer molding temperature (180° C.) and has an adhesivestrength under shear of 1 N/2×2 mm² to a 42 alloy plate, which wasrealized by providing an appropriate Tg or by selecting propercomponents, no weak adhesive layer is formed at the interface betweenthe sealer and the heat-resistant resin, so that the coating film showsexcellent sealer bondability and suffers no initial exfoliation, andfurther, no package cracking occurs in infrared reflowing after moistureabsorption, ensuring high package reliability.

EXAMPLE 6

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 73.90 g (0.18 mol) of2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter abbreviated toBAPP), 119.59 g (0.334 mol) of bis(3,4-dicarboxyphenyl)sulfonedianhydride (hereinafter abbreviated to DSDA), 17.78 g (0.117 mol) of1,3-diamino-5-carboxybenzene and 377 g of γ-butyrolactone (hereinafterabbreviated to BL) were supplied while blowing nitrogen gas through thesolution. After one-hour reaction with stirring at 50 to 60° C., thetemperature was raised to 195° C. and the reaction was allowed toproceed at this temperature for 5 hours. Water generated in the courseof the reaction was rapidly removed out of the reaction system. Theresulting solution was diluted with BL to obtain a polyimide resinsolution with a resin concentration of 40% by weight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 77.55 g (0.25 mol) of bis(3,4-dicarboxyphenyl)etherdianhydride (hereinafter abbreviated to ODPA) and 335 g of BL weresupplied while blowing nitrogen gas through the solution. Afterconducting the reaction with stirring at 50 to 60° C. for one hour, thetemperature was raised to 195° C. and the reaction was allowed toproceed at this temperature for 5 hours. Water generated during thereaction was rapidly removed out of the reaction system. The resultingsolution was diluted with BL to a resin concentration of 30% by weightand allowed to stand at 23° C. for one month. A solid polyimide resinfor filler containing the solvent was obtained.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 200 g of saidsolvent-containing solid polyimide resin for filler (resinconcentration: 30 wt %) in the pulverized form was supplied and heatedto 180° C. The resin was stirred at this temperature for one hour toform a homogeneous solution, and to this solution was added 300 g of thepreviously prepared polyimide resin solution (resin concentration: 40 wt%), followed by one-hour stirring at 180° C. The solution was cooled to23° C. over a period of about one hour and allowed to stand as such forone month. As a result, the fine particles of polyimide resin wereprecipitated and dispersed in the solution to form a paste. To thispaste, 27 g of γ-glycidoxypropyltrimethoxysilane (hereinafterabbreviated to GPS) was added and mixed well at room temperature, andthe mixture was diluted with BL to a resin concentration of 32% byweight to obtain a thermoresistance resin paste having a viscosity of250 Pa·s and a thixotropy factor (hereinafter referred to as TI value)of 2.8. The maximal size of the recovered polyimide resin particles was20 μm, and the particles were insoluble in BL at room temperature butsoluble at 150° C.

The above thermoresistance resin paste was bar coated on a glass plate(approximately 2 mm thick) to a coating thickness after heat drying of20 μm, and then heat dried at 140° C. for 15 minutes, at 200° C. for 15minutes and at 300° C. for 60 minutes to obtain a glass plate having apolyimide resin coating film. During this heat drying treatment,reaction of hydroxyl, amino or carboxyl group in the heat-resistantresin molecule with the crosslinking agent proceeded. This polyimideresin-coated glass plate was heated to 180° C., and about 0.1 g ofpellets of the sealer composing resins, i.e. a bisphenol epoxy resinYX-400H (trade name, produced by Yuka Shell Co., Ltd.), an orthocresolnovolak epoxy resin ESCN-190 (trade name, produced by Sumitomo ChemicalCompany, Ltd.), a phenolic novolak resin HP-850N (trade name, producedby Hitachi Chemical Company, Ltd.) and xylylene phenolic novolak resinXL-225 (trade name, produced by Mitsui Chemicals, Inc.) were placedseverally on the polyimide resin coating film of said glass plate andallowed to stand at 180° C. for 2 minutes. Thereafter, the molten resinleft on the polyimide resin coating film was wiped off at the sametemperature. A dissolubility test was conducted by observing thecondition (degree) of dissolution of the polyimide resin coating filmcaused by said resins. As a result, in the case of the orthocresolnovolak epoxy resin ESCN-190, there took place no change at all inappearance of the coating film, indicating that the coating film doesnot dissolve in this resin. In the case of the biphenyl epoxy resinXY-4000H, phenolic novolak resin HP-850N and xylylene phenolic novolakresin XL-225, although a trace of dissolution was admitted at theportion where the resin pellets contacted, there was observed noformation of hollows or holes in the coating film attributable to itsdissolution in these resins and consequent formation of a molten fluid.This indicates that said polyimide resin coating film does not dissolvein these resins.

The polyimide resin coating film was peeled off said coated glass plate,and the glass transition temperature (Tg) of this film (test piece: 3mm×20 mm) was measured by a thermophysical tester TMA-120 (mfd. by SeikoInstruments Inc.) under a load of 8 g and at a heating rate of 5°C./min. Tg was 265° C.

Said thermoresistance resin paste was bar coated on a silicon wafer(approximately 0.65 mm thick) to a coating thickness after heat dryingof 20 μm, and then heat dried at 140° C. for 15 minutes, at 200° C. for15 minutes and at 300° C. for 60 minutes to obtain a silicon waferhaving a polyimide resin coating film. This polyimider resin coatedsilicon wafer was diced into a 2 mm×2 mm silicon chip having a polyimideresin coating film. Said polyimide resin coated silicon chip was heatbonded to a Fe—Ni alloy (Ni content: 42%, hereinafter abbreviated to 42alloy) plate for lead frame with the polyimide resin coating filmserving as adhesive layer, under the conditions of 300° C., 0.2 MPa and5 seconds, and its adhesive strength under shear was measured by Dage'sautomatic adhesion tester Microtester BT-2 (measuring temperature: 25°C., testing rate: 0.5 mm/S). It was determined to be 10 N/2×2 mm².

Said thermoresistance resin paste was coated on the chip surfaceexcepting the bonding pad portion on a semiconductor substrate (wafer)by a screen printer (LS-34GX with aligning means, mfd. by NewlongSeimitsu Kogyo Co., Ltd.), and then heat dried at 140° C. for 15minutes, at 200° C. for 15 minutes and at 300° C. for 60 minutes toobtain a semiconductor wafer having a 20 μm thick polyimide resincoating film. This polyimide resin coated wafer (approximately 0.65 mmthick) was diced to obtain a semiconductor chip having a polyimide resincoating film. A 42 alloy-made lead frame 3 was heat bonded to thepolyimide resin coating film of said semiconductor chip as shown in FIG.2 under the conditions of 300° C., 0.1 MPa and 5 seconds. Then the leadframe and the semiconductor chip were joined by Au bonding wires andsealed by transfer molding with a biphenyl epoxy resin sealer CEL-9200(trade name, produced by Hitachi Chemical Company, Ltd.) 4. The adhesiveinterface between the polyimide resin coating film and the sealer of theobtained semiconductor device having the structure shown in FIG. 2 wasexamined by a supersonic flaw detector. There was observed noexfoliation at the interface (0/30, which indicates that none of the 30samples suffered exfolation). Also, when the semiconductor device(package) was allowed to absorb moisture by leaving it in an atmosphereof 85° C. and 85% RH for 168 hours and then subjected to infraredreflowing (240° C., 10 seconds), package cracking occurred in none ofthe 30 samples (0/30).

COMPARATIVE EXAMPLE 7

A heat-resistant resin paste having a viscosity of 210 Pa·s and a TIvalue of 3.3 was obtained in the same way as in Example 6 except that noGPS was added to the polyimide resin paste.

Using this thermoresistance resin paste, a glass plate having apolyimide resin coating film was obtained in the same way as in Example6. This film was homogeneous and transparent. Dissolubility of thispolyimide resin coating film in the sealer composing resins was examinedin the same way as in Example 6. As a result, the coating film dissolvedin any of the bisphenyl epoxy resin YX-4000H, orthocresol novolak epoxyresin ESCN-190, phenolic novolak resin HP-850N and xylylene phenolicnovolak resin XL-225 to form a molten fluid, which formed in the coatingfilm the holes of about 5 mm in diameter reaching the base glass plate.Tg of the coating film measured in the same way as in Example 6 was 236°C. Adhesive strength under shear of the coating film to a 42 alloy platemeasured by using said polyimide resin paste in the same way as inExample 6 was 17 N/2×2 mm².

Using said thermoresistance resin paste, a semiconductor device(package) was made in the same way as in Example 1 except that the pastewas print coated on the portion of the chip surface where the lead framewas to be bonded, other than the bonding pad portion, and the adhesiveinterface between the polyimide resin coating film and the sealer layerof said semiconductor device (package) was examined by a supersonic flawdetector. Exfoliation at the interface was observed in all of thesamples tested (30/30). Also, when the obtained semiconductor device(package) was allowed to absorb moisture by leaving it in an atmosphereof 85° C. and 85% RH for 168 hours and then subjected to infraredreflowing (240° C., 10 seconds), package cracking occurred in all of thesamples (30/30).

As is seen from the results of Comparative Examples 3 and 7 describedabove, a paste using a heat-resistant resin having no hydroxyl group inthe molecule or a paste made of a heat-resistant resin having carboxylgroup in the molecule but using no crosslinking agent falls short of thedegree of crosslinking and dissolves in the sealer composing resins atthe sealer molding temperature (180° C.) to form a molten fluid, and anew weak adhesive layer is formed at the interface between the sealerand the thermoresistance adhesive, so that the package suffers earlyexfoliation. Also, in infrared reflowing after moisture absorption,package cracking occurs. On the other hand, as is seen from the resultsof Examples 4, 5 and 6 described above, in the case of a paste providedwith appropriate Tg or prepared by selecting the proper components,moderate crosslinking is provided in the molecular structure, andtherefore such a paste does not dissolve in the sealer composing resinsat the sealer molding temperature (180° C.) and also its adhesivestrength under shear to a 42 alloy plate becomes greater than 1 N/2×2mm². Further, since no new weak adhesive layer is formed at theinterface between the sealer and the thermoresistance adhesive, sealeradhesion is enhanced and there takes place no early exfoliation of thepackage. Also, no package cracking occurs in infrared reflowing aftermoisture absorption, providing high package reliability.

EXAMPLE 7

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 65.69 g (0.16 mol) of2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter abbreviated toBAPP), 132.22 g (0.,40 mol) of bis(3,4-ddicarboxyphenyl)sulfonedianhydride (hereinafter abbreviated to DSDA), 38.84 g (0.20 mol) ofisophthalic acid dihydrazide, 9.93 g (0.04 mol) of1,3-bis(3-aminopropyl)tetramethyldisiloxane and 478 g of γ-butyrolactonewere supplied while blowing nitrogen gas through the solution. Afterone-hour reaction with stirring at 50 to 60° C., the temperature wasraised to 195° C. and the reaction was allowed to proceed at thistemperature. At the point when the number-average molecular weightbecame 27,000 (calculated as polystyrene), the reaction mixture wascooled to stop the reaction. Water generated during the reaction wasrapidly removed out of the reaction system. The resulting solution wasdiluted with γ-butyrolactone to obtain a polyamide resin (heat-resistantresin A) solution with a resin concentration of 30% by weight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 102.64 g (0.25 mol) of BAPP, 77.55 g (0.25 mol) ofbis(3,4-dicarboxyphenyl)ether dianhydride (hereinafter abbreviated toODPA) and 335 g of γ-butyrolactone were supplied while blowing nitrogengas through the solution. After one-hour reaction with stirring at 50 to60° C., the temperature was raised to 195° C. and the reaction wasallowed to proceed at this temperature. At the point when thenumber-average molecular weight became 28,000 (calculated aspolystyrene), the reaction mixture was cooled to stop the reaction.Water generated in the course of the reaction was rapidly removed out ofthe reaction system. The resulting solution was diluted withγ-butyrolactone to obtain a polyimide resin (heat-resistant resin B)solution for filler with a resin concentration of 30% by weight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 200 g of said polyimide resinsolution for filler (resin concentration: 30 wt %) and 466.67 g of saidpolyamide-imide resin solution (resin concentration: 30 wt %), bothfresh from the synthesis, were added, mixed and stirred at 180° C. forone hour to form a homogeneous transparent solution. The solution wascooled down to 23° C. over a period of about one hour and allowed tostand as such for one month, whereupon the fine particles of thepolyimide resin were precipitated and dispersed in the solution. Thissolution was diluted with γ-butyrolactone to obtain a polyimide resinpaste having a viscosity of 380 Pa·s and a thixotropy factor(hereinafter referred to as TI value) of 2.5. The maximal size of therecovered polyimide resin particles was 5 μm, and the particles wereinsoluble in γ-butyrolactone at room temperature but soluble at 150° C.

Said polyimide resin paste was bar coated on a glass plate(approximately 2 mm thick) to a coating thickness after heat drying of20 μm, and then heat treated at 140° C. for 15 minutes, at 200° C. for15 minutes and at 300° C. for 60 minutes to obtain a glass plate havinga cured polyimide resin coating film. The cured coating film wassubstantially homogeneous and transparent, indicating that the fineparticles of the polyimide resin (heat-resistant resin B) in thepolyimide resin paste are soluble in γ-butyrolactone and also compatiblewith the polyamide-imide resin (heat-resistant resin A).

EXAMPLE 8

The same synthesis procedure as described in Example 7 was conductedexcept that the amount of BAPP used was increased to 147.8 g (0.36 mol),and that no isophthalic acid dihydrazide was used to obtain a polyimideresin (heat-resistant resin A) solution having a number-averagemolecular weight of 28,000 (calculated as polystyrene).

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 102.64 g (0.25 mol) of BAPP, 77.55 g (0.25 mol) of ODPA and335 g of γ-butyrolactone were supplied while blowing nitrogen gasthrough the solution. After one-hour reaction with stirring at 50 to 60°C., the temperature was raised to 195° C. and the reaction was allowedto proceed at this temperature. At the point when the number-averagemolecular weight became 28,000 (calculated as polystyrene), the reactionmixture was cooled to stop the reaction. Water generated in the courseof the reaction was rapidly removed out of the reaction system. Theresulting solution was diluted with γ-butyrolactone to a resinconcentration of 30% by weight. Then the solution was cooled to 23° C.and allowed to stand as such, consequently giving a solid polyimideresin (heat-resistant resin B) solution for filler containing thesolvent.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 200 g of said solid polyimideresin for filler (resin concentration: 30 wt %), which has beenpulverized to particles, and 466.67 g of said polyimide resin(heat-resistant resin A) solution were added, mixed and stirred at 180°C. for one hour to form a homogeneous transparent solution. The solutionwas then cooled to 50° C. over a period of about one hour and stirred at50° C. for 3 days, whereupon the fine particles of the polyimide resinwere precipitated and dispersed in the solution. This solution wasdiluted with γ-butyrolactone to obtain a polyimide resin paste having aviscosity of 280 Pa·s and a TI value of 2.8. The maximal size of therecovered polyimide resin particles was 5 μm or less, and the particleswere insoluble in γ-butyrolactone at room temperature but soluble at150° C.

Using said polyimide resin paste, a glass plate having a cured polyimideresin coating film was obtained in the same way as in Example 7. Thecured coating film was substantially homogeneous and transparent,indicating that the polyimide resin particles in the polyimide resinpaste dissolved in γ-butyrolactone in the curing process and were alsocompatible with the polyimide resin (heat-resistant resin A).

EXAMPLE 9

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser provided with an oil/waterseparator, 89.09 g (0.217 mol) of BAPP, 119.59 g (0.334 mol) of DSDA,42.85 g (0.117 mol) of 2,2-bis(4-hydroxy-3-aminophenyl)hexafluoropropane(hereinafter abbreviated to HAB-6F) and 377 g of γ-butyrolactone weresupplied while blowing nitrogen gas through the solution. After one-hourreaction with stirring at 50 to 60° C., the temperature was raised to195° C. and the reaction was allowed to proceed at this temperature. Atthe point when the number-average molecular weight became 26,000(calculated as polystyrene), the reaction mixture was cooled to stop thereaction. Water generated in the course of the reaction was rapidlyremoved out of the reaction system. The resulting solution was dilutedwith γ-butyrolactone to obtain a polyimide resin (heat-resistant resinA) solution with a resin concentration of 40% by weight.

To a 1,000-ml four-necked flask equipped with a stirrer, a thermometer,a nitrogen gas inlet pipe and a condenser, 400 g of thesolvent-containing solid polyimide resin (heat-resistant resin B) forfiller (resin concentration: 30 wt %) obtained in Example 8 was suppliedin the pulverized form and heated to 180° C. The solution was stirred atthis temperature for one hour to form a homogeneous solution, to which300 g of said polyimide resin solution (resin concentration: 40 wt %)was added and stirred at 180° C. for one hour. Then the solution wascooled to 60° C. over a period of about one hour and stirred at thistemperature for one day, whereupon the fine particles of the polyimideresin were precipitated and dispersed in the solution to give a paste.To this paste was added 48 g of γ-glycidoxypropyltrimethoxysilane,followed by sufficient mixing at room temperature, and the mixture wasdiluted with γ-butyrolactone to a resin concentration of 36% by weight.The thus obtained polyimide resin paste had a viscosity of 150 Pa·s anda TI value of 3.5. The maximal size of the recovered polyimide resinparticles was 5 μm or less, and the particles were insoluble inγ-butyrolactone at room temperature but soluble at 150° C.

Using said polyimide resin paste, a glass plate having a polyimide resincoating film was obtained in the same way as in Example 1. This coatingfilm was substantially homogeneous and transparent, indicating that thepolyimide resin particles in the polyimide resin paste dissolved inγ-butyrolactone in the curing process and were also compatible with thepolyimide resin (heat-resistant resin A). Also, this coating film had athree-dimensional crosslinked molecular structure and was possessed ofexcellent solvent resistance as well as resistance to dissolution inepoxy resins at 180° C.

The following properties of the said paste were evaluated.

(1) Printability

Printing was made on a silicon wafer by a screen printer (LS-34GX withan aligning means, mfd. by Newlong Seimitsu Kogyo Co., Ltd.) using anickel alloy-made meshless metal plate (50 μm thick, pattern size: 8mm×8 mm, mfd. by Mesh Industry Co., Ltd.) and a Permalex metal squeegee(imported by Tomoe Kogyo KK), and printability was evaluated accordingto the following criterion:

Good: No blotting or broadening occurred, and good transfer was made.

Bad: Blotting and broadening occurred, and transfer was bad.

(2) Ionic Impurity Content

Na ions and Fe ions were determined by atomic-absorption spectroscopy.

(3) Number of Contaminants

In a clean bench of Class 100, the paste was bar coated on a glass plate(approximately 2 mm thick) to a coating thickness after heat drying of20 μm, and heat treated at 140° C. for 15 minutes, at 200° C. for 15minutes and at 300° C. for 60 minutes to obtain a glass plate having acured coating film. The number of the contaminants with a size of 20 μmor greater present in the area of 5 cm×5 cm of said cured coating filmwas determined by a microscope.

(4) Glass Transition Temperature (Tg)

The cured coating film obtained according to (3) was peeled off theglass plate, and the glass transition temperature of this film (samplesize: 3 mm×20 mm) was measured by a thermophysical tester TMA-120 (mfd.by Seiko Electronic Industry Co., Ltd.) at a heating rate of 5° C./minunder a load of 8 g.

The results are shown collectively in Table 3.

TABLE 3 Properties Example 7 Example 8 Example 9 Maximal size of resin 5or less 5 or less 5 or less particles (μm) Viscosity (Pa.s) 380 280 150TI value 2.5 2.8 3.5 Ionic impurity Na 0.9 0.6 1.0 content (ppm) Fe 1.00.8 0.7 Printability Good Good Good Number of 0 0 0 contaminants Tg (°C.) 256 270 260 Number of paste 3 3 3 producing steps

As is seen from the results of Examples 7 to 9, the thermoresistanceresin paste obtained according to the process of the present inventionexcels in forming thin films as the maximal size of the fine particlesof the heat-resistant resin B can be defined to 5 μm or less. Also,since the whole process for production of the paste can be conducted ina flask, the ionic impurity content is low and the number ofcontaminants is small, so that the paste is especially suited forsemiconductor applications. Further, the paste of this invention iseconomically advantageous as the number of its production steps can belessened.

INDUSTRIAL APPLICABILITY

The thermoresistance adhesive and thermoresistance adhesive solution ofthe present invention are useful as adhesive materials for semiconductordevices with high package reliability as such adhesive materials canafford high sealer adhesion and also no package cracking occurs ininfrared reflowing after moisture absorption.

The thermoresistance adhesive solution of the present invention, asworked into a paste, is capable of forming a thick-film, high-finenesspattern on a substrate by printing method, so that this adhesivesolution is high in productivity and useful as an adhesive material formanufacture of low-cost semiconductor devices. Further, in case thethermoresistance adhesive solution of this invention contains organicparticles for providing thixotropic properties, the organic particlesare compatibilized with the heat-resistant resin which becomes a binderwhen heated, making it possible to form a homogeneous film free ofpinholes or voids. Therefore, the obtained thermoresistance adhesive isuseful as an adhesive material for semiconductor devices with highreliability as such a thermoresistance adhesive has excellent moistureresistance, mechanical properties and α-ray shielding properties in useas a buffer coat for semiconductor chips. Further, the thermoresistanceadhesive solution of this invention, as worked into a paste, showsexcellent continuous printability and low-temperature curing propertiesdue to selective use of a solvent of high volatility and lowhygroscopicity, hence high environmental safety, such asγ-butyrolactone, so that it is useful as an adhesive material forsemiconductor devices with high productivity and reliability. Thethermoresistance adhesive and thermoresistance adhesive solution of thepresent invention have high adhesive strength under shear to lead frameand semiconductor chip, and are useful as an adhesive material forhigh-reliability semiconductor devices. The thermoresistance adhesive ofthis invention which does not dissolve at the molding temperature of 120to 200° C. has general-purpose properties and is useful as an adhesivematerial for semiconductor devices with excellent operatability andreliability.

The thermoresistance resin paste of the present invention is capable ofbonding (especially heat bonding) a chip and a lead frame and proofagainst package cracking in solder reflowing, can afford thixotropicproperties with no need of using any non-dissoluble filler such asinorganic filler, and is also capable of forming high-reliability,uniform thick-film pattern by screen printing. Further, thethermoresistance resin paste of this invention, by use of a solvent ofhigh volatility and low hygroscopicity, hence high environmental safety,is capable of realizing excellent continuous printability andlow-temperature curing properties as a paste, and is useful as anadhesive material for semiconductor devices with high productivity andreliability. Furthermore, the thermoresistance resin paste of thepresent invention enables formation of thick-film, high-fineness patternon the substrate, so that it useful as an adhesive material for low-costsemiconductor devices with high productivity.

The semiconductor chip having a thermoresistance adhesive layeraccording to the present invention has excellent productivity as thethermoresistance adhesive layer can serve as a buffer coat. Also, withthe semiconductor chip having a thermoresistance adhesive layeraccording to the present invention, it is possible to form athermoresistance adhesive layer with a high-fineness pattern by theprinting method with high coating efficiency, and as coating is madeonly on a specified area of the semiconductor chip unlike in theconventional spin coating method in which coating is made over the wholesurface of semiconductor wafer, it is possible to minimize warpage ofthe wafer and to offer the high-productivity, low-cost semiconductordevices.

The lead frame having a thermoresistance adhesive layer according to thepresent invention can be bonded to a semiconductor chip with a smallquantity of thermoresistance adhesive, making it possible to providelow-cost semiconductor devices.

The film having a thermoresistance adhesive layer according to thepresent invention makes it possible to offer a semiconductor devicewhich is minimized in contamination of connecting circuits and has highreliability as this film releases no volatile matter such as solventwhen heat bonded to a semiconductor chip.

The semiconductor device according to the present invention is proofagainst early exfoliation of package at the interface between the sealerand the thermoresistance adhesive and against package cracking ininfrared reflowing after moisture absorption, and thus has high packagereliability.

The thermoresistance resin paste producing process of the presentinvention is capable of imparting thixotropic properties to the pastewithout using a filler such as fine silica particles or non-dissolublepolyimide particles, can form a high-reliability, uniform thick-filmpattern free of voids or air cells by screen printing, and is furthercharacterized by minimized contamination with dirt and other ionicimpurities and high productivity. Thus, the process is capable ofproducing a thermoresistance resin paste which is suited for use as anadhesive for LOC of semiconductor devices, and as a layer insulatingfilm, protective film and adhesive for various types of wiring boardsand semiconductor devices.

What is claimed is:
 1. A process for producing a thermoresistance resinpaste, which comprises mixing (I) a heat-resistant resin A soluble in asolvent of (III) at room temperature and at a temperature used for heatdrying, (II) fine particles of a heat-resistant resin B which isinsoluble in the solvent of (III) at room temperature but soluble at atemperature used for heat drying, and (III) a solvent, heating themixture for dissolution, and cooling the obtained solution to deposit ordisperse the fine particles of the heat-resistant resin B of (II) in thesolution of the heat-resistant resin A of (I) and the solvent of (III).2. The process according to claim 1, wherein the fine particles of theheat-resistant resin B of (II) are deposited and dispersed in thesolution of the heat-resistant resin A of (I) and the solvent of (III)with the maximal size of said resin B particles being defined to 10 μmor less.
 3. The process according to claim 1, wherein the heat-resistantresin A is a polyimide resin or a precursor thereof, a polyamide-imideresin or a precursor thereof, or a polyamide resin.
 4. The processaccording to claim 1, wherein the heat-resistant resin B is A polyimideresin or a precursor thereof, a polyamide-imide resin or a precursorthereof, or a polyamide resin.
 5. The process according to claim 1,wherein the heat-resistant resin A is a polyimide resin or a precursorthereof, a polyamide-imide resin or a precursor thereof, or a polyamideresin and the heat-resistant resin B is a polyimide resin or a precursorthereof, a polyamide-imide resin or a precursor thereof, or a polyamideresin.